Mr. F. A. Bather on British Fossil Grinoids. 3 1 1 



visceral cavity. Its great size compared with the lower cup, 

 the presence of large numbers of small pores, and the position 

 of the anal aperture near the bottom instead of at the summit, 

 seems \_sic] to imply that the anal apparatus occupied in the 

 internal economy of this sac only a limited space. The inflated 

 sac can accordingly not be homologized with the slender, 

 heavy plated tube of Actinocrinus. We can only com- 

 pare its lateral opening, which is generally placed low 

 down near the arm-bases, with the anal aperture of species 

 in which the anus is located in the ventral disc." In 1879 

 Messrs. Wachsmuth and Springer add* to this, that the 

 plates are thin, that " the pores perforate the plate at 

 each angle," that " in some species there are in place of the 

 pores slit-like fissures of considerable length " which they 

 compare with hydrospires of Cystidea, and that the anal 

 opening is " rarely observed, evidently lateral — not posterior 

 — and low down." To this view of the ventral sac they have 

 since adhered (Rev. III. (83), Proc. 1835, p. 305). It is, 

 however, difficult to distinguish any pores or slits in the 

 common Cyathocrinus of our Wenlock Limestone, which 

 appears to be identical with G. acinotubus of Angelin f, 

 neither do Angelinas figures of Cyathocrinus alutaceus, G. 

 glaber, C. muticus, and G. ramosus show any trace of pores. 

 Further, I have been unable to find any anal opening in the 

 best preserved specimens of Gissocrinus in the British Mu- 

 seum, which are the only specimens displaying its supposed 

 position that have come under my notice. I am not aware 

 that the anal opening of any Fistulate has as yet been figured 

 or even definitely described. It is possible that the anal 

 opening is at the distal extremity of the sac after all, but that 

 its minuteness, and the closing of the plates around it after 

 death have prevented its recognition. Even with recent 

 Crinoids, as Dr. P. H. Carpenter tells me, a similar difficulty 

 is often experienced. But these slight objections, supposing 

 them to prove well founded, would hardly disturb the main 

 contention of Messrs. Wachsmuth and Springer, that the 

 ventral sac of the Fistulata is a peculiar organ unparalleled in 

 other groups. Besides promoting excretion it probably sub- 



* " Revision of the Palaeocrinoidea, Part I." (pp. 9 and 60), Proc. Ac. 

 Nat. Sci. Philadelphia, 1879, pp. 232 and 283. In future this work will 

 be referred to as " W. & S. Revision,' and the pages of the authors' copies 

 given in brackets ; the reference to the Proceedings will be indicated 

 thus, " Proc. 1879, p. 232." 



+ II. Trautsehold places the ventral sac of C. acinotubus with that of 

 the ordinary Actinocrinus type (" Ueber den muthmasslichen Geschlechts- 

 apparat von Potcriocrinus multiplex, Trd.," Festschrift k. Gesell. Natur- 

 forscher, Moscow, 1882). 



