PLATE XVIII. 



Page 

 Ptychockixus PAKvas (Hall) 199 



Fis- 1". View of the specimen described by S. A. Miller as Gli/ptocrinus (inf/ularis 

 (f). (Coll. S. A. Miller.) 

 1/j. Another specimeu with the arms better preserved ('{). (Same collection.) 

 2. The specimen described by Wetherby as Glyptocriims (Reteocrinus) gracilis 

 Cf). (Coll. ilr. Vaupel.) 



Ptychockinis splendens (Miller) 198 



3/. The type specimen (^). (Coll. S.A. Miller.) 

 '6h. Another specimen (f). (Same collection.) 



TlIYSANOCKINUS LILIIFOKMIS Hall 192 



4. The type specimen. (Museum of Cornell University.) 



Thysanocbinus occidentalis (Hall) 194 



5«. Side view of calyx (?). (After Hall.) 

 M. Posterior view of calyx. (After Hall.) 

 5f. Dorsal aspect of calyx C{). (After Hall.) 



TlIYSANOCRIXU.S INORNATUS (Hall) 193 



Gil. Anterior view of calyx. (Coll. W. F. E. Gurley.) 



G'/. Posterior view of same specimen. 



()c. Ventral aspect of same (f). 



Cvl. A. young specimen, probably of this species. (Same collection.) 



Thysaxocrinus brachiatus (Hall) 195 



7. Dorsal aspect of the type specimen ; the matrix removed so as to show the 

 pinnules and the arrangement of the plates. (Am. Mus. Nat. Hist. N. Y.) 



Idiocrinus elongatus W. and Sp 203 



8rt. The type specimen; side view. (Coll. W. and Sp.) 

 8.''. Ventral aspect of same ({*). 



8c. Another view of the ventral disk (t). (Anal side to the right. Coll. W. 

 and Sp.) 



Idiocrinus ventricosus W. and Sp ... 205 



9«. The type specimen ; side view. (Same collection.) 



96. Dorsal aspect of the dorsal cup. (Anal side to the left. Same collection.) 



Idiocrinus immaturus (Hall) 206 



10a. The type specimen; anterior view. (Am. Mus. Nat. Hist. N. Y.) 



IQb. Posterior view of same. 



10c. Dorsal aspect of same. (After Hall.) 



Idiocrinus tennesseensi.s (Worthen) 206 



11. The type specimen. (Illinois State Collection.) 



