A MONOGRAPH OF THE EXISTING CRINOIDS 19 



through a predominence of pressure on one side of the anal plate as the latter is 

 lifted out from between the radials. There is no such torsion in Decametrocrinus, 

 and it might be inferred that in the young of species of this genus a plate similar to 

 the radianal occupies all the interradial areas. This occurs in Thaumatocrinus, 

 which resembles Pentametrocrinus and Decametrocrinus in its arm structure, and it 

 may well be that the young of Pentametrocrinus and Decametrocrinus will be found 

 to be very similar to, or identical with, Thaumatocrinus. 



The anomalous pinnulation of Uintacrinus is explained by assuming the presence 

 of two distichals (IIBr elements) beyond each costal (IBr) axillary of which the 

 outer is not an axillary. The arm of Uintacrinus from the costal axillary onward is 

 therefore comparable to the entire arm in Eudiocrinus, with the location of the first 

 brachial syzygy between the fourth and fifth brachials of the definitive arm as in 

 the Pcntametrocrinidae. Mr. Springer has figured a specimen of Uintacrinus 

 socialis in which the second postcostal ossicle is an axillary, and another in which 

 the second postradial ossicle, normally the first (costal) axillary, is not axillary. A 

 third specimen figured by him has the first pinnule on the inside instead of on the 

 outside of the arm, and lacks the first distichal (IIBrj). In the young of Uintacrinus 

 the second distichal (IIBr 2 ) has distinctly the appearance of an axillary ossicle. 



Mr. Frank Springer had purchased from Mr. Alan Owston of Yokohama the 

 collection of recent crinoids which he had been gradually assembling as a result of 

 the dredging operations of his yacht the Golden Hind. The stalked crinoids (Meta- 

 crinus rotundus) he retained for his own collection, turning over the comatulids to 

 the author by whom they were deposited, in Mr. Springer's name, in the National 

 Museum. 



Among the comatulids there was a 5-armed species entirely different in appear- 

 ance from Eudiocrinus varians, E. japonicus and E. tuberculatus which was at once 

 recognized as being closely related to Eudiocrinus indivisus and at the same time 

 related to the Japanese species of Zygometra, Z. hartlaubi, Z. rubroflava, and Z. 

 koehleri. So important did this discovery seem at the time that a preliminary note 

 dividing the genus Eudiocrinus as understood by Carpenter into two sections, Eudio- 

 crinus sensu stricto and Pentametrocrinus, was incorporated in a paper then in course 

 of preparation on a further revision of the old genus Antedon, which was published 

 on April 11. A more detailed paper dealing with the genus Eudiocrinus written at 

 the same time was published on June 20. 



In this paper the genus Eudiocrinus was carefully analyzed and separated into 

 its component elements, the species indivisus, granulatus and variegatus (sp. nov.) 

 being left in Eudiocrinus, s. s., and atlanticus, japonicus, semperi, tuberculatus, and 

 varians being assigned to Pentametrocrinus. 



The family Zygometridae was redefined and enlarged to include Zygometra and 

 Eudiocrinus, and the family Pentametrocrinidae was made to include Pentametro- 

 crinus, and Decametrocrinus. 



Eudiocrinus variegatus, sp. nov., was described in detail, and a cirrus and the 

 pinnules on either side of the base of the arm figured. 



The arm structure of the 10-armed comatulids and of the Eudiocrinus indivisus 

 and E. japonicus groups is described in detail, and that of E. indivisus and its allies 



