ECHINONEUS CYCLOSTOMUS. 51 that of a one-sided sphaeridium (fig. 3) from the odd anterior ambulacrum which contrasts with the circular chipped outline (fig. 4) and its ovoid mate, from the left anterior ambulacrum. Dissimilarity is also observable (fig. 6), where the first sphaeridium is ovoid and the other club-shaped; both came from the right anterior ambulacrum of a specimen 26 mm. long.
It is noticeable that the five figures on Pl. 17, figs. 7-9, are not exactly like those on Pl. 16, figs. 1-4, although the specimens came from the same place, Fakarava Island. It should, however, be observed that they were taken from two specimens, one 12 mm. the other 23 mm. in length.
ARRANGEMENT OF THE TUBERCLES AND SCROBICULAR CIRCLES.
Plates24,25.
De Loriol mentions the tubercles and scrobicular circles as specific characters.' In perfect specimens, on the actinal side near the actinostome in the interambulacral area, the primary tubercles may be for the most part without a scrobicular area, but surrounded by large glassy tubercles. In other specimens of the same size, from the same locality, the boss is deeply set on the test, and the serobicular circles are transformed to open angular cells, with a small number of miliaries and a few minute glassy tubercles on their edges. (Pl. 25, fig.9.)
The primary tubercles on the actinal side are nearly uniform in size and arranged in horizontal rows. <A few of the plates nearest the actinostome have a single line, after this each plate has two; in the region of the ambitus, and for some distance above, the tubercles run diagonally as well as horizontally, and they vary in number according to age. They are smallest in the odd posterior interambulacrum.
The seventh plate from the actinostome, including the primordial, in the left anterior interambulacrum of eight specimens from Port Antonio, measuring from 4.19 mm. to 17 mm. in length (with an interval of about two millimetres between each) is shown on PI. 25, figs. 7-8. In the smallest specimen, 4.19 mm. in length (fig. 1), this plate is on the abactinal side, and has, besides a few miliaries, only two of the primary tubercles, one being towards the upper corner near the median line. In the next smallest, 6 mm. long, this seventh plate (fig. 2) is on the actinal side, and has its third tubercle near the upper outer corner; all 1TwospecimensfromMauritius,36and37mm.inlength,resembledeLoriol’sE.abnormalis, butthemameloniswithoutaperforation.
52 TROPICAL PACIFIC ECHINI.
three are grouped in a triangle with the base upwards. These three first primaries are recognizable in fig. 3 (8 mm.), and fig. 4 (10 mm.), the latter having an increase of two primaries in the lower part, one being towards the outer side, the other near the median line. In fig. 5 (12 mm.), the seventh plate is not quite normal, but it shows the same regularity. When a length of about 15 mm. (fig. 6) is reached, the upper row has four primaries, one of the new comers being near the outer margin, the other, which is the smallest near the median suture. In a test of 17 mm. (fig. 7), and an adult of 26 mm. (fig. 8), there is no increase of the primaries, but they are arranged as previously described. The miliaries vary in number. The glassy tubercles are minute, few, and frequently absent.
While there are only four of the primary tubercles in the upper row in these specimens, Pl. 25, figs. 1-8; when the test is broadly ovoid with a length of 35 mm. or so, they have gradually increased to eight or more. A comparison of the primary tubercles on the ambulacrum in specimens of various sizes and different localities shows a regular order in their appearance. The odd anterior ambulacrum was selected for illustration, and in the extensive material examined from Port Antonio, there was no deviation so long as the specimens were normal. The smallest specimen, 6 mm. in length (PI. 24, fig. 7), has two rows of primary tubercles, one on each side of the ambulacrum adjacent to the ambulacral pores. The first primary of the next line, the third, has its seat in front of the fourth tubercle from the actinal system as shown, Pl. 24, fig. 1-7. This third row in fig. 2, test 8 mm. long, curves towards the left side of the ambulacrum, to make room for the fourth which commences on the right side near the second tubercle of the third row, as seen in fig. 3, a test of 9.5 mm., and fig. 4, test 11 mm. long. A fifth row has its first tubercle above or close to the third primary of the fourth line, as in two specimens, 16 and 18 mm. long, figs. 5 and 6. The latter specimen (18 mm.) has the sixth or last row to the right of the fifth, beginning at the right of the first tubercle in the fifth row. Some of the central rows extend only to the actinal and abactinal region of the ambitus. The odd anterior ambulacrum of a test 27 mm. long, from the Pacific (fig. 7), shows exactly the same number of rows and order of grouping in the primary tubercles as is seen in those from Jamaica. The glassy tubercles are mostly ovoid, with their lower half in the test, flattened at the top with corrugated sloping sides, armed with small sharp points (Pl. 25, figs. 11, 12). They are either colorless, or of a blackish tint, until freed from the test when they become transparent.
ECHINONEUS CYCLOSTOMUS. 53 THe PEDICELLARIAE.
Plates18-23;Plate26,figs.16-19,30,31;Plate27,figs.12,13,23,24,35,36,43,44. How great the variation of shape can be in pedicellariae of the same kind, taken from the same specimen, but from different parts of the test, is shown in the illustrations (Pls. 18-23) which are few when compared with the material available. To distinguish which valve of the three in any one pedicellaria is meant, since they are not of equal height, or the same form of loop, I have used in addition to Mortensen’s comprehensive terminology, the letters A, B, C; A, denoting the highest, C, the lowest, and B the intermediate valve. The tridentate pedicellariae are few in number, and found only on the actinal side of the test, near or a short distance from the oral and anal systems. Of three valves from the same pedicellaria (Pl. 18, figs. 1-6), from a specimen 34 mm. long, from Lord Howe Island, no two of them have outlines exactly alike. The blade in valve A (fig. 2), at the upper part is ellipsoidal, and does not correspond to valve B (fig. 3), where it is circular; while in valve C (fig. 5), it is slightly pointed. We find the same irregularity in the base, which either slopes, or has a sharp prolongation on the right or left side close to the neck. A valve of another pedicellaria (Pl. 18, figs. 70, 11), has no indication of the articular loop, and the blade is possibly broken. Presumably it is a young tridentate pedicellaria.
For uniformity one of the series valve B, was chosen for comparison. Three such valves (Pl. 18, figs. 7, 9), from a specimen 15 mm. long from Makemo Island, were taken respectively from near the actinostome in the odd posterior interambulacrum, from the odd anterior ambulacrum, and from the right anterior interambulacrum. The obvious difference in the form of the blades, which vary from a triangular point to a round top, in the variation in number of lateral teeth from 11 to 15 in each blade, and in the shape of the neck and bases, is most striking. They are very unlike those on PI. 20, figs. 8, 10-13, also from Makemo Island specimens. I find no specific identity between two valves (PI. 20, figs. 8 and /0), from the same specimen, 10 mm. long; one valve from the aboral end of the anal system, the other from midway between the actinostome and the ambitus, in the right posterior interambulacrum. In one of these the blade and base are of nearly the same height, while in the other the outline of the base is rounded, the long neck abruptly narrowed, and the blade short with indications of lateral teeth. In valve C (fig. 11), from another specimen 11 mm. long, these lateral teeth are very conspicuous. The same striking difference is observ-
o4 TROPICAL PACIFIC ECHINI.
able in a valve B (fig. 12), and a valve C (fig. 13), from a specimen 18 mm. long; in the former the blade and base are of about the same size, while in the latter the base is diminished in size and deltoid in shape. When selecting valves for illustration from a number of specimens from Fakarava Island, ‘‘ Albatross”? Exped. 1899-1900, I decided, after some hesitation, upon figures to show the greatest extremes in form; thus Pl. 19, fig. 5, valve B, with a triangular base, has a remarkably long neck and minute blade without serrations, and this has little similarity to a valve A (Pl. 19, fig. 2), with serrations and large lateral teeth, or to a valve B (fig. 3), with its large ovoid blade, comparatively short neck, and rounded outline of the base, which in valve C (fig. 4), is irregular. In connection with these it is interesting to note that in a specimen from Barbados, 26 mm. long, I find some of the tridentate valves (PI. 19, fig. 7), showing the character of those from Fakarava Island (Pl. 19, figs. 1-4). The only dissimilarity is in the outline of the base, which in the specimen from Barbados, is armed close to the neck on both sides with large prolonged points.
Between three specimens 11, 12, and 13 mm. long, and one 19 mm., all from Fakarava Island, I should not expect to find great dissimilarity, but valves A, B, C, from the same pedicellaria in the smallest specimen, have broad rounded blades with large lateral teeth and stout symmetrical bases, which including the articular loop, are as long as the blade. Their form has no similarity to a valve B (PI. 20, fig. 5), from midway between the actinostome and the ambitus in the right anterior interambulacrum, or to another valve B (PI. 20, fig. 6), from near the actinostome in the right anterior interambulacrum, which has a long deltoid base, and short triangular blade; neither is it like another valve B, (Pl. 20, fig. 7), from the adoral end of the anal system. Even fig. 9, a valve B, with its well-marked lateral teeth differs from the others. The material from Port Antonio shows still further diversity as seen in a comparison of nine valves of the series B, one of them (PI. 23, fig. 12) from the odd posterior interambulacrum, actinal side, near the ambitus, with its broad neck which gradually unites to the blade, contrasts with one (fig. 73) from the aboral end of the anal system, in which the blade is nearly circular. Both valves are of equal height, and from the same individual, measuring 25 mm. in length. I find another case of a valve (fig. 14) from the adoral end of the anal system of a specimen 26 mm. long, where the remarkably large base is almost square, the blade broad and short, and ending in a sharp point; this is quite unlike a valve (fig. 15), from the left posterior interambulacrum near the
ECHINONEUS CYCLOSTOMUS. 55 actinostome from a spetimen 28 mm. long, which has the edge of its long neck bent inward like a collar, and which in turn contrasts to figs. 9-17, Pl. 23. The first one from a specimen measuring 11 mm. in length, and the two latter from one 20 mm. long. In a young specimen of 4 mm., the valve B (fig. 1), from the | anal system, and (fig. 2), from the right posterior ambulacrum, near the actinostome, already have a difference in their shape.
It should be noted that tridentate pedicellariae (figs. 17—26) were owing to insufficient space on the preceding plates placed on Pl. 22. The specimens were from the Paumotu Islands, South Pacific, and from the West Indies, and the figures readily show their diversity in shape.
The ophicephalous pedicellariae are the most numerous, especially on the abactinal side, and they vary the least in form. Three valves, same pedicellaria (Pl. 21, figs. 3, 4, 6), from the left posterior interambulacrum, of the actinal side of the ambitus, from a specimen 34 mm. long, from Lord Howe Island can be regarded as typical; but a large number deviate as will be seen in valve C (fig. 7), and valve A (fig. 8), from the actinal side of the ambitus in the right posterior interambulacrum, and especially in valve A, with its long slender neck and articular loop pointed at the lower end. Of course a difference in shape is to be expected between pedicellariae from the abactinal side of the test, or near and on the apex, and those from the actinal side. This is shown in two valves, B (fig. 9), and C (fig. 10), of the same pedicellaria, from near the apical system of a 30 mm. specimen when compared with the figures referred to above. In valve B which is practically of the same height as that shown in fig. 4, the blade with a broad apophysis passes into the base almost without any neck; the articular loop is stout and sharp pointed at its lower end; the articular teeth are wide, and the articulation surface slopes to the left where the loop is thickest; this is reversed in the other (fig. 4), where it slopes to the right; this reversal is a common occurrence. Two valves, B and GC, in height 0.16 mm., from the apical system, of a specimen 11 mm. long, from Fakarava Island (PI. 21, figs. 17, 12), do not present any great deviation from two others, B and C, 0.21 mm. in height from the actinal side of a specimen 15 mm. long, from Makemo Island, (figs. 13, 14).
Of three valves, the same pedicellaria from the right posterior ambulacrum, near the anal system, from a specimen 30 mm. long, from Barbados (Pl. 21, figs. 15, 17), the blade has lost its discoidal form, and passes into the base almost without any neck. The loop is that of an ophicephalous pedicellaria, but the base and blade are exactly those of a tridentate form, and this may be noted even in valves (figs. 18—20), from the abactinal side up to the apical system.
56 TROPICAL PACIFIC ECHINI.
One might regard this as a specific character for the West Indian species, but it is not characteristic of those from Jamaica. Two valves, A and B (PI. 23, figs. 3, 4), from the odd posterior interambulacrum, near the anal system, in a young specimen 4 mm. long, from Port Antonio, resemble those of a typical ophicephalous pedicellaria. :
The globiferous pedicellariae were found only near the ambitus, and on the abactinal system in the two specimens from Lord Howe Island, and in a small specimen from Fakarava Island; besides these there were some near the summit in the two individuals from Barbados, and in the specimens from Jamaica. These pedicellariae (Pl. 22, figs. 1-16, Pl. 23, figs. 5-8), are essentially alike in the different specimens, although they vary more or less in outline. In three valves of the same pedicellaria, from the left anterior ambulacrum, on the actinal side toward the ambitus, the pointed blade is nearly as long as the base (Pl. 22, figs. 3-6), with twelve strong lateral teeth on each blade, except C, which has only eleven. In other valves examined, the number of the lateral teeth in A and B, vary from nine in the smallest to thirteen in the largest, valve C generally having one less. From the right posterior interambulacrum, at the ambitus, in valves A and C (figs. 8, 9), height 0.26 mm., the blades are round at their upper ends, and about one third the length of the base, while in two other valves B and C, 0.34 mm. in height (figs. 10, 11), from towards the apical system, the blades are longer, and the bases broader at the articulation surface. Another (fig: 12), valve B, height 0.32 mm. from near one of the genital plates, has assumed the form of those on the actinal side. All these pedicellariae came from the same specimen, 34 mm. long, from Lord Howe Island, N. 8. Wales.
When the distance between the localities, and the difference in length of the two specimens (one 34 mm. from N. 8. Wales; the other 19 mm. long, from Fakarava Island) is considered, it is singular that the pedicellariae do not apparently show any real differences (see figs. 13, 14, two valves, A and B, from the right posterior interambulacrum of the latter). Attention should be called to the slenderness of the valves (Pl. 22, figs. 15, 16), in a specimen 30 mm. long, from Barbados, when compared with a valve of a 4 mm. specimen from Jamaica, (Pl. 23, fig. 5); in the latter it is nearly triangular, with a minute blade and rounded base. This difference might be considered important if another valve (Pl. 23, fig. 6), from the same part of the ambitus and from the same Jamaican specimen was not shaped like those from Lord Howe Island and if it was not also unlike two valves (figs. 7, 8), in a specimen 5 mm. long, from Jamaica.
ECHINONEUS CYCLOSTOMUS. 57 The articular loop in valve A is short, straight, and generally has two foramina; in valve B, the loop is prolonged either at the right or left side (Pl. 22, figs. 4, 14), with a single foramen, while in valve C, the articulation surface slopes downward, and the loop is rudimentary.
The triphyllous pedicellariae were found only in the Jamaican specimens (Pl. 23, figs. 16, 17), and mostly in the ambulacra near the actinostome. Even in the adult specimens they are very small, 0.04 mm. in height; the bilobed blade constitutes the largest part of the valve.
A comparison of the height of the pedicellariae to the length of the test from which they were taken, shows that in young specimens they are proportionally larger than in the adult. Where a tridentate pedicellaria is 0.13 mm. in height on a 4 mm. specimen, it is only 0.51 mm. from a test 34 mm. long. The stalk of the pedicellariae differ in form on different parts of the test. One stalk (Pl. 26, fig. 31), of an ophicephalous pedicellaria, near the actinostome, from a specimen 18 mm. long from Makemo Islands, with its long rod, ending in a head, is similar in form to one of the same order from the actinostome of an adult specimen (PI. 27, fig. 36), from Jamaica. In a specimen 34 mm., from Lord Howe Island, on the abactinal side towards the apex (PI. 26, fig. 19), the stalk is thicker, and without a head, corresponding to one (PI. 27, fig. 13), on the abactinal side of a specimen 23 mm. long, from Fakarava Island. The stalks of the globiferous pedicellariae have peculiar processes, similar to those of some spatangoids, as figured by Mortensen ‘‘Ingolf’’ Exped. Ech., pt. 2, pl. 17, 18). Otherwise they show little diversity, though one (PI. 26, fig. 17) from near the apical system of a Pacific specimen, 34 mm. long, is more solid than some others. The latter are shown on Pl. 27, one (fig. 24) from the abactinal surface of a specimen from Barbados, 30 mm. long, and another (fig. 44) from a Jamaican specimen only 4 mm, long.
THE SPICULES OF THE TUBE-FEET.
Plate28,figs.1-14.
No special difference was found in the tube-feet (Pl. 28, figs. 1-14), though a large number of specimens from the Pacific and also the West Indies were studied. They all agree in having a disk composed of three plates, but the number may vary, as Lovén has shown (Pourtalesia, Pl. 11, fig. 117). In some the periphery of the plates is lobed (PI. 28, figs. 5, 6, 13), but usually it has an irregular ragged outline, as seen in Pl. 28, figs. 8, 9, 12, 14; figs. 8 and 9
DS TROPICAL PACIFIC ECHINI.
are from West Indian specimens, figs. 72 and 74 from specimens taken in the Pacific.
At the smaller inner end, the plate (PI. 28, figs. 5, 6, 12) is prolonged slightly beyond the adjoining surface in some of the Makemo and Jamaican specimens. This is quite different from what is seen in a Barbados specimen, where the projection can easily be recognized, though placed in a reéntrant curve (Pl. 28, figs. 8, 9). In another specimen from Fakarava Island the inner end of the plate (PI. 28, fig. 14) is almost straight.
Close to the base of the disk on the lower side there is a set of two or more layers of yoke-shaped spicules (Pl. 28, figs. 2, 3, 7); these are nearly straight with a few small perforations on the inner side of the spicule. The tube-feet on the actinal, and on the greater part of abactinal side, seem to be without any other spicules, but in some of the tube-feet near the ocular plates a number of slender rods (fig. 10) were found; the disk plates were only rudimentary. The changes in the appearance of the disk may be due as much to their position on the test as to growth, as may be seen in three Jamaican specimens. In a specimen 25 mm. long the tube-feet of the actinal side, near the mouth (fig. 5) with disks 0.22 mm. across, are very different from those near the apical system (fig. 6) with disks only 0.14 mm. wide. But-in much younger specimens, the first formed tube-feet (fig. 4) which are found close to the mouth, are similar to the newly formed ones near the ocular plate. Apparently the difference between figs. 17, 12, from the actinal side of the test, and fig. 73, from near the ocular plate, in the specimen from Makemo, is due to difference in age. THe PERIPODIA.
Plate28,figs.15-24.
A comparison of the peripodia in a number of specimens, both young and adult, from various localities, does not reveal any reliable specific character, as the shape of the peripodium changes in form, size, and position on the different plates.
Of four peripodia (Pl. 28, figs. 15-18), from a specimen 34 mm. long, from Lord Howe Island, the first one at the edge of the actinostome (fig. 15), is singly perforated, and placed vertically on the plate. The fifth from the actinostome, (fig. 16), with its great horizontal perforations, is the largest; the smallest is attached to the ambitus, and is placed diagonally on the outer part of the plate. These and one of the youngest peripodia near the ocular plate, with its oval