180 



p. HERBERT CARPEKTER. 



tion ' tKat many Palceocrinida and Cystidea have remained 

 permanently in this condition appears to me to be an ex- 

 ceedingly happy one, as far as the former group is concerned, 



■Tftt' 



Fig. XIII. — Seation through a Pentacrinoid with a closed teutacular ves- 

 tibule, the mouth uot having yet broken through to the exterior. 

 (After Gotte.)^ ae. Ambulacral epithelium. al. Alimentary 

 canal. an. Rudiment of anus, marking the position of the blasto- 

 pore. Ip. Posterior division of the left peritoneal sac, from which 

 the subtentacular canals are derived. Ip'. Its anterior division, 

 forming the tentacular vestibule. ;«. mouth. mt. Mesentery, 

 separating the cavities of the right and left peritoneal sacs. r. 

 Roof of the tentacular vestibule = vault of FalcBOcrinoidea. rp. 

 Right peritoneal sac, giving rise to the greater part of the body cavity. 

 rp'. Its posterior extension into the developing stem. t. Tentacles. 

 v>r. Watervascular ring. 



though I do not think it applicable to the Cystids with 

 grooves on the *'vault." It gives us a complete explanation 

 of their subtegminal mouth, the presence of which has been 

 so successfully demonstrated by Wachsrauth/ in accordance 

 with Schultze's suggestion.* Thus, in many Palaeozoic 

 genera the mouth is permanently subtegminal, while in the 

 more modern forms it is only temporarily so during the 



1 Loc. cit., p. G37. 



2 See Plate xxvi, fig. 19, of Gotte's paper. 



3 Loc. cit., pp. 116, 120. 



4 Loc. dt., n. 7 (119). 



