236 BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



" Challenger " report makes a key to the species of the genus very desirable, 

 especially since Dr. Carpenter in his key only included the three species dis- 

 covered by the " Challenger" and the " Porcupine," omitting the interesting form 

 dredged by the " V0ringen." In the preparation of the following key I have 

 examined specimens of all the species given, with the exception of B. aldri- 

 chianus. There are two additional species as yet undescribed, one dredged by 

 the " Valdivia" off Enderby Land, and the other from the Atlantic coast of the 

 United States. 



Key to the species of Bathycrinus. 



A. Basal ring squarish, or wider than high. 



a. basal ring with straight or concave sides ; columnars markedly " dice- 

 box shaped," the articulations prominent; 10-25 short discoidal colum- 

 nars at summit of stem. 



b. arms perfectly smooth, brachials not overlapping. 



c. costals and brachials low and rounded, non-carinate. 



d. first brachials as long as or longer than wide; columnars 

 short, 25 or more at summit of stem wider than high. 



(Northern and northeastern Atlantic) 



B. carpenterii (Danielssen and Koren). 



dd. first brachials wider than long ; columnars long, 15 or 



less at summit of stem wider than high. (Northwestern 



Pacific) B. complanatus A. H. Clark. 



cc. costals distinctly carinate ; brachials high, compressed, and 

 carinate. (Near the Crozet Islands). B. australis A. H. Clark. 

 bb. brachials with raised and prominent distal edges, imparting a 

 serrate appearance to the arms, 

 c. costals with a strong, rounded, median keel. 



d. lower part of radial funnel much constricted. (Equatorial 



Atlantic). B. aldrichianus Wyville Thomson. 



dd. radial funnel slopes evenly downward from the upper to 



the lower edge. (Coasts of southern Europe) 



B. gracilis Wyville Thomson. 

 cc. costals with no trace of a median keel. (Off southern Japan). 



B. pacificus A. H. Clark. 

 aa. basal ring with markedly convex sides ; columnars cylindrical ; five short 



discoidal columnars at summit of stem. (Equatorial Pacific) 



B. equatorialis, sp. nov 

 AA. Basal ring markedly longer than wide. (Caribbean Sea). B. caribbeus, sp. nov. 



The following table gives the bathymetrical, thermal, and geographical range 

 of each species of Bathycrinus, and of the genus as a whole, as now known ; but 

 the data given will doubtless be greatly modified by future discoveries, as but one 

 species, B. carpenterii, can be considered to be even approximately understood ; 

 it is probable that the geographical range, even of this species, is much greater 

 than that given, and there may be a corresponding lack of information in regard 

 to the limits of the thermal and bathymetrical altitudes inhabited by it. 



