388 clakk: bourgueticrinidae 



ZOOLOGY. — A revision of the recent genera of the crinoid fa?nily 

 Bourgueticrinidae, with the description of a new genus. 1 

 Austin H. Clark, National Museum. 



Of all the families of stalked crinoids represented in the re- 

 cent seas the Bourgueticrinidae is the most universally distrib- 

 uted, occurring in all the oceans and ranging from 112 meters 

 (62 fathoms) or less to a depth of 4842 meters (2690 fathoms) , 

 the greatest depth at which stalked crinoids have been found. 



The genus Metacrinus, now dominant in the East Indies and 

 ranging from southern Australia and Tasmania to southern 

 Japan, includes about 25 species; but aside from this genus the 

 Bourgueticrinidae with its 30 species is more numerously repre- 

 sented than all the other stalked families together. 



Heretofore the recent species of Bourgueticrinidae have been 

 grouped in two genera, Rhizocrinus and Bathycrinus, though it 

 has long been evident that such a disposition was far from 

 satisfactory; especially has this been the case since the discov- 

 ery of the species of Monachocrinus, which have the general 

 appearance of the species of one of the genera (Bathycrinus) , but 

 the detailed structure of those of the other (Rhizocrinus) . 



The recent species of the Bourgueticrinidae fall into six nat- 

 ural groups, which are differentiated as shown in the following 

 key: 



Key to the Recent Genera belonging to the Family Bourgueticrinidae 



a 1 The third, sixth, and ninth brachials (the fifth, eighth, and eleventh 

 ossicles from the radials) have a muscular articulation on either 

 end; basals always fused into a solid ring which is broader than long, 

 cylindrical or short truncated-conical; ten arms 



b 1 The distal edges of the brachials are produced, overlapping the 

 bases of the succeeding brachials, so that the dorsal profile of 

 the arms is serrate; the IBr 2 (axillary) is markedly broader than 

 long, distinctly shorter than the IBri 



Bathycrinus. 

 b 2 The distal edges of the brachials are not produced, so that the 

 dorsal profile of the arms is smooth; the IBr 2 (axillary) is little, 

 if any, broader than long, and is about as long as the IBri 



Ilycrinus. 



1 Published with the permission of the Secretary of the Smithsonian Institu- 

 tion. 



