NAmiACHOCRINUS, A NEW GENUS BELONGING TO THE 

 CRINOID FA]\IILY PHRYNOCRINID^. 



By AusTix IIoBAKT Clark, 



Assistant Curator, Diinsion of Marine Invertebrates, United Stales National Museum. 



T\\e genus Plirynocrinus,^ basctl upon u single species describetl from 

 i\ single specimen dredged by the United States Fisheries steamer 

 Albatross oft' southern Japan in 190G,- represents a unique ty])e of 

 crinoid structure, though its more or less distant relationship to the 

 genus Rhizocrinus is evident. So extraordinary are the characters 

 presented by tliis animal that at the time of its description a new- 

 family, Phrynocrinida^, -was created for its reception. 



Recently in looking over some material from the Hawaiian Islands 

 a curious crinoid was found which at first sight appeared to be a 

 BJiizocrinus of the R. rawsonii type, but with the distal third of the 

 stem of the Phrynocrinus type, devoid of radicular cirri and attached 

 to a terminal stem ]:)late. Analysis of the calyx of this new form, 

 however, shows that the calyx, instead of being composed of enor- 

 mously elongated basals bearing distally small radials as in Rhizo- 

 crinus, is just the reverse, the very small basals bearing cm their 

 distal edge enormously elongated radials. This type of calyx 

 structure is quite unique. Certain species of Bathycrinus have very 

 short basals; but in this genus whenever the basals are short they 

 are always fused into a solid ring — and they are never so short as in 

 Phrynocrinus and in this new species. The radials of Bathycrinus, 

 though usiialh' longer than the radials of Rhizocrinus, never become 

 elongated as in this form, ^lany species of Rhizocrinus, and especially 

 of Bathycrinus, possess more or less phrynocrinoid distal extremities 

 to the stem, but in all cjises they possess radicular cirri, never being 

 attached. But this difference, though interesting, is of no great 

 importance, for in certain groups, and even in single genera, some 

 forms may be free with radicular cirri, while others are attached to a 

 heav)- terminal stem plate. 



■ For the author, place and date o( publication, derivation, etc., of this and the other crinoid names 

 herein Riven see Proc. U. S. Nat. Mas., vol. 34, pp. 435-542. 

 » Proc. U. S. Nat. Mus., vol. 32, p. 507, fig. 1, p. 508. 



Proceedings U.S. National Museum, Vol. 42— No. 1895. 



195 



