344 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



the costals and lower brachials, characteristic of the "Basicurva," 

 "Spinifera," and "Granulifera" groups, is equally well marked in 

 species of the "Milberti," "Tenella," and "Palmata" groups, and 

 in species closely allied to Antedon balanoides. Since the pub- 

 lication of the Challenger report, the family Comatulidae, as under- 

 stood by Dr. Carpenter, has been broken up into the families 

 Thaumatocrinidae (Thaumatocrinus) , Antedonidae (including Eudio- 

 crinus, Antedon, and Thiolliericrinus) , Atelecrinidse (Atelecrinus) , 

 Actinometridse (Comatula), and Decametrocrinidse (Promacho- 

 crinus and Decainetrocrinus). The family Decametrocrinidse ap- 

 pears to be somewhat unnatural. Decainetrocrinus is most nearly 

 related to Eudiocrinus, and it is doubtful if single arms from 

 species of the two genera could be differentiated; Decainetrocrinus 

 is clearly a meristic variation from a Eudiocrinus type. The two 

 genera agree in having the disk black, the perisome extending 

 far up on the arms, in having single undivided arms, and per- 

 fectly smooth cirri with elongated segments ; the first two charac- 

 ters do not occur in any other genera of free crinoids, while a de- 

 tailed study of the cirri will probably prove them to be quite as 

 characteristic. Another point is that the ambulacra in Eudiocrinus 

 and Decainetrocrinus do not divide upon the disk; in the former 

 there are five ambulacra running from the mouth to the arms, and 

 in the latter ten, arranged in five pairs. Taking these points into 

 consideration, it appears most logical to unite Decainetrocrinus and 

 Eudiocrinus, making of them the family Eudiocrinidse, from which 

 combination Proinachocrinus is omitted. I only know Promaclw- 

 crinus from what has been written of the genus, having had no 

 opportunity of examining specimens ; and it therefore seems best 

 not to say anything about it for the present, more particularly as we 

 shall soon hear something in regard to it from one of the foremost 

 authorities on the recent crinoids. Attention should here be called 

 to the researches of Mr. Frank Springer on Uintacrinus and its 

 probable relationship with the genus Comatula. 



Turning our attention again to the genus Antedon, we find that 

 it has been revised by Hartlaub in 1895, an d by Minckert in 1905. 

 The former divided Antedon into groups with, and without, plated 

 ambulacra, but otherwise followed Carpenter. Minckert, in his in- 

 structive work on the arm regeneration in the comatulids, uses Car- 

 penter's groups, but proposes another group, the "Brevipinna 

 group," for species with plated ambulacra, and variable (2 or 4 

 (3 + 4) or both) distichal series. Both authors take Carpenter's 

 groups as homogeneous units, which in many cases thev are not; 



