MEM. M. C. Z., IX. No. 2. — ECHINODERMATA. 37 



15, 16. MuUita kmyijissa. 

 1'). Young siiccimi'ii, iiiitiiral size, in which the notches forming the ambulacral hinules coniineiiee to close, .seen 

 from the aliaotinal side. 



16. Part of test of a young specimen, about J of an incli iu diameter, in wliich the ambulacral lunules hare com- 



pletely closed ; seen from the abactinal side. 

 17-22. Echiiuirachnius parma. From Alexander Agassiz, Eevision of the Echini, Part II., 1872, PL XII. 



Quoted above. 



17. Young specimen (•^i'^), seen in profile, elongated Echinometra-like stage. 



18. The same as fig. 17, seen from the abactinal side ; the anus at this stage opens ahove the ambitus. 



19. Somewhat older stage (f ), seen from the abactinal side ; the anal opening is placed nearer the ambitus. 



20. Older than the preceding stage (i), seen from the abactinal side; the outline has become somewhat more 



elliptical. 



21. Older stage, seen from aliove (f ). In the abactinal part of the aml.iuhii la the pores have bocome conjugated. 



22. Still older stage, seen from above ( '^~) ; the abactinal part of the ambulacra has become slightly petaloid ; 



the anal opening is partly on the ambitus. 

 23, 24. Encopc emanjinata. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XII. 



Quoted ahove. 



23. Young specimen in the Moulinsia stage (^i^), showiug the first trace of the posterior interambulacral lunulc 



on the actiual -side. 

 2i. Young Encope, natural size. The posterior interambulacral hinulehas forced its way through from the actinnl 

 to the abactinal surface, and there are traces of the lateral ambulacr.al notches, which are to form the 

 lunules (which may remain closed or open) of the older stages. 

 26-29. Gonolampas SUjsbei. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XVI. 



Quoted above. 



26. Young specimen, seen from the abactinal side, partly denuded. 4 mm. in diameter. 



27. 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. Jlemiaslcr cavernosus. From Alexander Agassiz, Report on the Ecliinnidea of the "Challenger," 1881, 



PI. 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 rhe Mode of Propagation of certain Echinoderms of the Southern Sea. Journ. Linn. Soc. Zoology, XIII., 

 1876, p. 70, fig. 9. 



31. Young, 2 mm. in diameter, taken from the pouch of the petaloid ambulacra, still somewhat circular, with 



str.aight primary spines, seen from the abactinal side. 



32. Somewhat older than the preceding stage, 3 mm. in diameter ; the test carries curved primary spines, seen 



from the abactin.al pole. 



33. Young, in about the stage of fig. 32, denuiled 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 fiisciole ; seeii from the abactinal side. 

 36, 36'. Spatangus purpurens. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XI'. 



Quoted above. 



36. Young specimen, seen from the abactin.al side (J), showing the straight simple ambulacra of the future 



petaloid system of the abactinal part of the test. 

 36'. Tlie actinostome of the same ; the posterior actinal lip is as yet scarcely developed. 



37-40. Bri^sopsin lyrifcra,. From Alexander Agassiz, Revision of the Echini, Part II., 1872, PI. XIX. 



Quoted above. 



37. Young Brissopsis, measuring 5.6 nan. in iliameter, 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 snbanal fasciole. 



38. 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 tlie lateral aujbu- 



lacra somewhat petaloid. 



