254 NATURAL SCIENCE [April 



a character which, as Carpenter has shown, is of no classificatory 

 vahie ; the species belong to our type C and the names are therefore 

 synonyms of Isocrinus. Chladocrinus, L. Agassiz (1835), was 

 separated from Pentacrinus of Miller in these words : " On pourrait 

 designer sous le nom de Chladocrinus les especes dont les rayons 

 accessoires forment des verticilles plus ou moins distans." De 

 Loriol and Carpenter suppose the word " rayons " to refer to the cirri 

 of the stem ; but this makes the sentence a mere repetition of " tige 

 portant de distance en distance des rayons simples, verticilles," 

 which is given as a character of Pentacrinus. I suggest that 

 " rayons " refers to " rayons du disque," i.e., arms, which may, 

 as Agassiz says, " se ramifier en de nombreux appendices pinn^s 

 a leurs bords " ; these appendices or accessory branches are, surely, 

 the armlets of our type B. On this view the sentence has a 

 meaning that does not insult the intelligence of Agassiz, while the 

 name Chladocrinus is appropriate and antedates Extracriiius, Austin. 

 At the same time it is a synonym of Pentacrinus {sens. str.). Hetero- 

 crinus, 0. Fraas, has been quoted more than once as a synonym of 

 type B. Fraas (1858) did distinguish between two types of 

 branching, " Isocrine " and " heterocrine " ; but he carefully ex- 

 plained that he did not intend to propose any new generic name, 

 and he doubtless knew well enougli that the name Hcterocrinus was 

 preoccupied by J. Hall. 



The conception of Pentacrinus here maintained has been urged 

 by no less an authority than Sir C. Wyville Thomson (1864). 

 Keferring to P. caput-medusae, he says : " Another and a widely 

 different species, Pentacrinus hriareus, from the Lias of the South 

 of England, seems, however, to have a just claim to be recognised as 

 the type of the genus Pentacrinus." For P. cajnit-medusac and one 

 or two fossils which closely resemble it. Sir Wyville therefore pro- 

 posed the name Ccnocrinus. In no case could this name be ac- 

 cepted, since it has the same derivation as Cainocrinus, Forbes ; and 

 whichever be the correct spelling, in that way should both be written. 

 This question, however, does not arise, since both were anticipated by 

 Isocrinus. In the same paper Sir Wyville proposed the separation 

 of Pentacrinus decorus and allied species as a subgenus, Neocrinus ; 

 but the need for this step has been denied by Carpenter. 



The conclusions to which we are brought concerning the names 

 applicable to types B and C are as follows : — 



B. — Pentacrinus, Blumenbach, 1804; Type, P. fossilis ( = P. 

 hritannicus, Schlotheim ; P. hriareus, Miller). Synn. Poly- 

 cerus, peers, Waldheim, 1811; Chladocrinus, Agassiz, 1835 ; 

 Extracrinus, Austin, 1847. 

 C. — Isocrinus, Von Meyer, 1837; Type, I. pendulus { = Penta- 

 crinus amblysccdaris, Thurmann ?). Synn. Isis, pars. 



