1886.] NATURAL SCIENCES OP THILADELPHIA. 79 



radials ^ are comparatively large, and rest upon the upper face of 

 the main part of the radials ; in Synibathocrinus small, placed 

 against the distal ends of their limbs, and separated by radial 

 dome plates. In the Haplocrinidoe the anal opening penetrates 

 one of the interradials, and also probably in Pisocrinus, Stor- 

 thingocrinus and Stylocrinus ; in Symbathocrinus and Fhimo- 

 crinus it is placed along the suture of two adjacent muscle-plates. 

 This position of the anal opening between the muscle-plates is a 

 peculiarity found exclusively among the Larviformia ; we meet 

 with it again in Cupressocrinidse, and in a somewhat different 

 form among Gasterocomidse. 



The Cupressocrinidse and Gasterocomidae are dicyclic Crinoids, 

 containing within their basal ring an undivided plate in form of 

 a disk. The disk is pierced by sevei'al large openings, a central 

 one which represents the axial canal, and by four (exceptionally 

 three or five) peripheral ones, which are continued to the whole 

 length of the column. The other two families have only a central 

 opening, which is small. Dr. P. H. Carpenter, whom we consulted 

 as to the functions of these openings, thinks it " very probable 

 that the periplieral ones represent downward extensions of the 

 body cavity in which water circulated ; while there was an exha- 

 lant or outgoing current through the interradial (so-called anal) 

 opening with which the intestine was related, so that faecal matter 

 could be carried away from the creature, very much as it is by the 

 circulation through the dorsal and ventral siphons of a Solen or 



The specimens for which Hall (18G2, 15th Rep. N. Y. St. Cab. 

 Nat. Hist.) proposed the name Ancyrocrinus are evidently 

 crinoidal stems with four peripheral canals, and as such may 

 belong to Myrthillocrinus or some other genus of this family. 

 There are at the lower end four lateral appendages, which in our 



^ If the five ventral plates in Haplocrinus and the allied Allagecrinus 

 were orals, as Dr. P. H. Carpenter suggests, it would follow that these 

 two genera exceptionally had no interradials, and vary on this point from 

 all other Palseocrinoidea. To this we had reference on p. 72, but in place 

 of stating, as we intended, "Carpenter denies the interradials to he present 

 always in Palseocrinoids," we made the erroneous statement: "C. denies 

 that interradials are present as a rule in Palaeozoic Crinoids." The correc- 

 tion was made throughout our own edition, but we discovered the error 

 too late to rectify it in the Proceedings of the Philadelphia Academy. 



