CLARK! BOURGUETICRINIDAE 389 



a 2 All the post-radial ossicles are united in pairs by non-muscular ar- 

 ticulation; the basals are separate, or are fused into a solid ring 

 which is truncated conical, always longer than broad 



b l Ten (or twelve) arms, the second post-radial ossicle being 

 axillary 



M onachocrinus . 

 b 2 Five undivided arms 



c 1 No sutures visible between the basals; the basals are solidly 

 welded into a single conical ossicle 



Rhizocrinus. 

 c- Basals, always separated by distinct sutures 



d 1 Column comparatively slender, the longer columnals be- 

 ing at least twice as long as broad; calyx distinctly conical 



Bythocrinus. 

 d 2 Column very stout, the longer columnals being but little 

 longer than broad ; calyx nearly or quite cylindrical 



Democrinus. 



.Bathycrinus Wyville Thomson. 



Bathycrinus Wyville Thomson, Proc. Roy. Soc. Edinburgh, 7, 1872, 

 p. 772 (genotype B. gracilis, sp. nov.). 



Geographical Range. — Mid-equatorial Atlantic and northwestward to 

 the coast of Virginia and Maryland (as far as 38° 20' N. lat.), and north- 

 ward to the latitude of the northern part of the Bay of Biscay (47° 38' 

 N. lat.); eastern part of the Bay of Bengal, east of the northern end of 

 Sumatra; mid-Pacific between Oceania and America (from 0° 3'.4 to 

 9° 57' N. lat,). 



Bathijmetrical Range.— From 1629 to 4842 meters (905 to 2690 

 fathoms). 



Thermal Range.— From 34?3 to 36?8 Fahr. (all but one of the rec- 

 ords are between 36?5 and 36?8). 



Included Species. — Bathycrinus aldrichianus Wyville Thomson, Bathy- 

 crinus equatorialis A. H. Clark, Bathycrinus gracilis Wyville Thomson, 

 Bathycrinus pacificus A. H. Clark, Bathycrinus serratus A. H. Clark, 

 Bathycrinus sibogae A. H. Clark, and Bathycrinus woodmasoni A. H. 

 Clark. 



Ilycrinus Danielssen and Koren. 



Ilycrinus Danielssen and Koren, Nyt Magasin for Naturvidens- 

 kaberne, 23, 1877, 3 die Hefte, p. 45 (genotype /. carpenterii, sp. 

 nov.) 



Pterocrinus (Wyville Thomson, MS.) P. H. Carpenter, "Challenger" 

 Reports, Zoology, 11, 1884, p. 242, 243 (genotype Bathycrinus aldri- 

 chianus P. H. Carpenter, 1884 [not of Wyville Thomson, 1878] = 

 Bathycrinus australis A. H. Clark, 1907). 



Geographical Range. — Antarctic regions, from west of the Crozet 

 Islands to Enderby Land; extreme north Pacific from the Commander 



