MEM. M. C. Z., IX. No. 2. — ECHINODERMATA, DT 
15, 16. Mellita longifissa. 
15. Young specimen, natural size, in which the notches forming the ambulacral lunules commence to close, seen 
from the abactinal side. 
16. Part of test of a young specimen, about } of an inch in diameter, in which the ambulacral lunules have com- 
pletely closed ; seen from the abactinal side. 
17-22. Echinarachnius parma. From Alexander Agassiz, Revision of the Echini, Part II., 1872, Pl. XII. 
= Quoted above. 
17. Young specimen (42), seen in profile, elongated Echinometra-like stage. 
18. The same as fig. 17, seen from the abactinal side ; the anus at this stage opens above the ambitus. 
19. Somewhat older stage (#), seen from the abactinal side ; the anal opening is placed nearer the ambitus. 
20. Older than the preceding stage ({), seen from the abactinal side; the outline has become somewhat more 
elliptical. 
_ 21. Older stage, seen from above (#). In the abactinal part of the ambulacra the pores have become conjugated. 
22. Still older stage, seen from above (3:3); the abactinal part of the ambulacra has become slightly petaloid ; 
the anal opening is partly on the ambitus. 
28, 24. Encope emarginata. From Alexander Agassiz, Revision of the Echini, Part II., 1872, Pl. XI. 
Quoted above. 
23. Young specimen in the Moulinsia stage (7,2), showing the first trace of the posterior interambulacral lunule 
on the actinal side. 
24. Young Encope, natural size. The posterior interambulacral lunule has forced its way through from the actinal 
to the abactinal surface, and there are traces of the lateral ambulacral notches, which are to form the 
lunules (which may remain closed or open) of the older stages. 
26-29. Conolampas Sigsbei. From Alexander Agassiz, Revision of the Echini, Part II., 1872, Pl. XVI. 
Quoted above. 
26. Young specimen, seen from the abactinal side, partly denuded. 4mm. in diameter. 
7. The same, seen from the actinal side ; the anal opening is on the sloping posterior edge of the ambitus of the test. 
28. The same, seen in profile, showing the position of the anal system. 
29. Young specimen, in its Echinolampas stage, measuring 12.7 mm. in diameter ; seen in profile. 
30-35. Hemiaster cavernosus. From Alexander Agassiz, Report on the Echinoidea of the ‘‘ Challenger,” 1881, 
Pl. XX*. Quoted above. 
30. One of the lateral ambulacral petals of a gravid female, showing the mode in which the young embryos are 
carried in the deeply sunken petaloid ambulacra. From C. Wyville Thomson, Notice of some Peculiarities 
in the Mode of Propagation of certain Echinoderms of the Southern Sea. Journ. Linn. Soc. Zoology, XIII, 
1876, p. 70, fig. 9. 
31. Young, 2mm. in diameter, taken from the pouch of the petaloid ambulacra, still somewhat circular, with 
straight primary spines, seen from the abactinal side. 
32. Somewhat older than the preceding stage, 3mm. in diameter ; the test carries curved primary spines, seen 
from the abactinal pole. 
33. Young, in about the stage of fig. 32, denuded of spines, showing the simple ambulacral pores, the large anal 
opening, within the broad peripetalous fasciole, and the ring of large primary tubercles, forming its inner 
edge ; about 3 mm. in diameter. 
34. The same as fig. 33, somewhat less magnified, seen from the actinal side. 
35. Young Hemiaster, measuring 5.5 mm. in diameter; the anal system is now removed from within the peri- 
petalous fasciole to the outer edge of the broad peripetalous fasciole ; seen from the abactinal side. 
36, 36!. Spatangus purpureus. From Alexander Agassiz, Revision of the Echini, Part II., 1872, Pl. X1% 
Quoted above. 
36. Young specimen, seen from the abactinal side (?), showing the straight simple ambulacra of the future 
petaloid system of the abactinal part of the test. 
36’. The actinostome of the same ; the posterior actinal lip is as yet scarcely developed. 
37-40. Brissopsis lyrifera. From Alexander Agassiz, Revision of the Echini, Part II., 1872, Pl. XIX. 
Quoted above. ? 
37. Young Brissopsis, measuring 5.6 nim. in diameter, from the abactinal side ; shows the huge ambulacral ten- 
tacles (provided with suckers) of the odd ambulacral area, within the slightly dumb-bell-shaped peripetalous 
fasciole. ‘The anal system is placed between the posterior edge of the abactinal and of the subanal fascicle. 
88. Profile of same, showing the bevelled anterior extremity of the test, surrounded by the peripetalous fasciole. 
39. Peripetalous fasciole of a young specimen, measuring about 3.6 mm. in longitudinal diameter ; 5 : 4 pairs of 
simple pores in the anterior, and 4:3 pairs in the posterior lateral ambulacrum. There are from five to six 
simple pores in the odd anterior ambulacrum. 
40. Peripetalous fasciole of an older stage, in which the fasciole has become undulating, and the lateral ambu- 
lacra somewhat petaloid. 
