PLATE XVIII. 



Page 



Ptychocrixus parvus (Hall) 199 



Fig. la. View of the specimen described by S. A. Miller as Glyptocrinus angularis 



(»). (Coll. S. A. Miller.) 

 lb. Another specimen with the arms better preserved (f). (Same collection.) 

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



(§). (Coll. Mr. Vaupel.) 



Ptychocrixus splendexs (Miller) 198 



3». The type specimen (f). (Coll. S.A. Miller.) 

 3b. Another specimen (f). (Same collection.) 



Thysanoceixus liliifoemis Hall 192 



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



Thysanocrinus occidentalis (Hall) 194 



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

 5b. Posterior view of calyx. (After Hall.) 

 5c. Dorsal aspect of calyx (f). (After Hall.) 



Thysanocrixus inorxatus (Hall) . . 193 



6a. Anterior view of calyx. (Coll. W. F. E. Gurley.) 



6''. Posterior view of same specimen. 



6c. Ventral aspect of same (f). 



6d. A young specimen, probably of this species. (Same collection.) 



Thysanocrixus beachiatus (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.) 



Idioceinus eloxgatus W. and Sp 203 



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

 8&. Ventral aspect of same (-p). 



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

 and Sp.) 



Idioceinus venteicosus W. and Sp ... 205 



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



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



Idioceinus immaturus (Hall) 206 



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



10b. Posterior view of same. 



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



Idiocrinus texxesseensis (Worthen) 206 



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



