LARVIFORM CRINOIDS 



37 



place. The following table summarizes the distinguishing characters of the 

 various genera : 



Displacement of Displacement of 



oral plates anal opening 



Left Right Left Right 



Hemistreptacon Jakovlev 12° 12° 



Coenocystis Girty 36° 36° 



Acariaiocrinus Wanner 36° 0° 



Dichostreblocrinus J. M. Weller, n. gen. 9° 12" 



Tytthocrinus Weller, n. gen. 0° 24° 



Dichostreblocrinus scrobiculus J. M. Weller, n. sp. 

 Plate II, figs. 9a-d 



Fig. 8 



Plan of the calyx of Dichostrehlocrinus 

 scrobiculus 



Description. — The holotvpe has a height of 1.78 mm. which is about one 

 and a half times its greatest breadth. The calyx is subpyriform with a sub- 

 circular, subpentagonal cross-section. It is composed of three rings of plates, 

 (1) a small infrabasal disc, (2) five approximately equal basals, and (3) five 

 subequal orals. 



The form and size of the infrabasal disc is not known as the sutures 

 separating it from the basals are not distinguishable, but it probably makes 

 up about one-sixth of the total height of the calyx. From the moderately 

 sized stem facet pierced by a single central opening it slopes upward and 

 outward to the basals. 



The basal plates constitute about two-thirds of the height of the calyx. 

 They are wider above than below, sharply truncated above and probably sub- 

 oval below, and their height is equal to about one and one half times the 

 greatest width. Each basal plate bears a longitudinal more or less broadly 

 rounded ridge from which the plate slopes away on either side to join its 

 neighbors in the flat or gently concave lateral sides of the calvx. The basal 

 plates are rather regularly and uniformly shaped but the longitudinal ridges 

 are commonly somewhat inclined to the axes of these plates and thus produce 



