DISCOVERY OF THE DISK OF ONYCHACRINUS 517 



ii. RA rhomboidal, obliquely to left of r. post. R. 

 Primibrachs 2 (exceptionally I). 

 Arms dichotomous; IBr 2 or i. 



Anal X alone, or followed by others in series. . Lecanocrinns 



(Cyrtidocrinus) 

 h. No radianal. 

 Primibrachs 2. 



Arms dichotomous. 



Anal X with triangular plate above; arms with dex- 

 trorse twist Mespilocrimis 



c. No anal nor radianal. 

 Primibrachs 2. 



Arms dichotomous Metichthyocrinus , 



Primibrachs 3. 



Arms dichotomous. 



(Anal side unknown, but from form of calyx probably 



not distinct) (/• greenei) .... 



Rays separated all around by interbrachial plates Sagenocrinid.^e 



a. Radianal. 



I. Anal area more or less completely filled by solid plates, 

 forming part of calyx wall. 



i. Large anal x alone, or followed by others in single series. 

 Arms more or less contiguous. 

 Primibrachs 2 or less. 



RA more or less under r. post. R., above the line of 

 BB; iBrfew. 



Arms dichotomous Anisocrinus 



Arms heterotomous 



RA variable, either between BB or absent. 

 Infrabasals very large, enveloping BB. 



Arms dichotomous with ramules inside 

 dichotom; iBr few. 

 10 main arm-trunks; RA generally 



present H omalocrinus 



20 main arm-trunks; RA generally 



absent Calpiocriniis 



Arms more or less divergent. 



RA rhomboidal, obliquely to left of r. post. R. 

 Arms dichotomous; IBr generally i. 



iBr areas wide, occupied by small, irregular 

 plates; IBr not filling distal face of RR 



Pycnosacus 

 Arms heterotomous; 10 main arm-trunks 

 with ramules inside dichotom; iBr areas wide; 



IBr not filling djstal face of RR. 



(L. obesus n. g.) Cholocrinns 



