CHAPTER III. 



Branch ECHINODERMATA. 



Class CRINOIDEA. 



Order ARTIGULATA. 



Family BOITRGUETIORINIDAE. 



Genus Rhizocrinus Sars. 



Rhizocrinus cylindricus n. sp.^ 



Plate VI., Fig. I. 



Description.— Calyx cylindrical, slender and greatly elongate, 

 the sides almost straight, not enlarging from the basals up. The 

 proximal column joint (or joints?) higher than the basals and 

 radials together, cylindrical above with straight sides, slightly 

 ■contracted beloiw. Basals much higher than the radials. Radial 

 facets shallow, curved, rather wide, separate, low and not sloping 

 upward, having no conspicuous muscle plate or ligament fossa. 

 They enclose a relatively large and well excavated central funnel 

 ■or visceral cavity. 



The dimensions of the type specimen are : height of proximal 

 ■column joint and calyx together, 9.3 mm.; diameter, 3 mm.; 

 height of proximal column joint, 6 mmi. 



Remarks. — This species is established on a single complete calyx 

 and proximal stem joint, although numerous isolated column 

 joints may belong to the same species. The specimen is clearly 

 a member of the family Bourgeticrinidae, and superficially 

 resembles, in some respects, Bourgueticrinus ellipticus and B. 

 ■aequalis from the white chalk of England, but it differs from 

 these species in the much greater height of the basals. The char- 

 acter of the radial facets and the large visceral cavity, however, 



' The writer is indebted to Mr. Frank Springer for valuable suggestions re- 

 .^garding the relationship of this species. 



(275) 



