30 DK. P. H. CARPENTER ON CERTAIISr POINTS 



side, above plate 15 ; for his figures of E. armatus on pis. xviii. 

 and xix. show that it is on the left side above plate 18, i. e. in 

 interradius DE. He assigned a similai- position to the anus or 

 " reniform groove " of Apiocystis pentremitoides ; but Hall* was 

 " unable to observe the reniform groove or pore on the right side 

 near the apex *' of A. elegans, while he found one, or possibly 

 two, on the left side above the plate which, he marked 16, though 

 I sKould call it 18, as I have already pointed out. Hall took 

 these to be the mouth and anus. But what he called the " single 

 straight groove in the direction of the back and front of the body " 

 is now known to be the linear peristome containing the mouth ; 

 and should the second opening described by him really exist, we 

 must, I think, regard it as excretory, while the otter, if present, 

 may be genital. The same remark applies to Callocystis, in 

 which the peristoraial plates of interradius DB are pierced, ac- 

 cording to Hall t, by the mouth and anal pore, and also bear a 

 little porous tubercle which " strongly reminds one of the madre- 

 poriform tubercle in Asterias and other Echinoderms." 



Eurther information about these structures is much to be 

 desired, and it is quite j)ossible that the " porous tubercle " of 

 Callocystis may be of the same doubtful nature as the similarly- 

 named structure which Hall described a few pages further on in 

 Semicystis, though later writers have made no allusion to it. 

 Another of Hall's genera, Sphcerocystis %, has a small opening 

 close to the peristome in the same interradius DE. It also occurs 

 in Glyptocysiis multipora, as described and figured by Billings §, 

 while Loveu marked it as the genital aperture in Angeliu's 

 figure of the summit o£ Cryptocrinus Icevis ||. 



I am inclined to think that in all these genera with no separate 

 genital opening in interradius CD, wbich seems to be its normal 

 position, there was a common osculum for the anus and genital 

 ducts, as in Hymenaster ; while the lateral opening in interradius 

 DE was excretory in function. Indeed, one might almost 

 say that it represented a madreporite, and also placed the 

 water-vascular system in communication with the exterior. The 

 presence of this aperture in the same position in seven of those 

 genera which have a pentamerous and dicj^clic dorsal cup like that 



* ' PalEeontology of New York,' vol. ii. p. 243, pi. li. figs. 7, 8. 

 t Ibid. pp. 238, 240. 



X ' Palteontologj of New York,' vol. iii. p. 130, pi. vii. A, figs. 1-5. 

 § Loc. cit. p. 56, pi. iii. fig. ly. || Ojo. cit. tab. xii. fig. 3. 



