J29. CONTRIBUTION TO 



ventral roof as a tunnel. It will be observed that Nucleocriniis has a ventral 

 disk as in Sehizoblastus but wanting the outer pyramid of Fentremites. 



Figure 55 is a ventral view of a melon-shaped specimen, whose ambulacra 

 traverse low, canoe-sha])etl elevations and stand out beyond the surface of those 

 areas. 



The surface ornamentation is beautifully preserved and the ventral cover- 

 ing plates in [)lace. 



This specimen varies enough from the typical jY ver/ie it tli to he considered 

 specifically distinct, if its characters were constant in a series of specimens; 

 but the gradual passage of typical vei'iieaill into this form through intermedi- 

 ate varieties can be traced in a series of Nucleocrinus from the Falls. Our 

 S])ecinien may be identical with Harris' X. iiielonifoinnis,. 



Figure 50 is an enlarged view of a group of hydrospires beneath an ambu- 

 lacrum. I'he characteristic number is four. The side plates and the lancet 

 plate are outlined just over the hydrospires, while parts of two inter-ambulacral 

 areas are shown. 



All of these specimens of ^V. vernea'di are from the Middle Devonian beds 

 at the J'^ills of the Ohio. 



N U C L E O ( ' R 1 N U S G K E E N E 1 , M. & G. Rowley. 



Plate 36. Fig. 57. 



We give iiere an inverted basal view of a specimen to show the slightly 

 elevated basal cu]). 



Upper Devonian beds near Charlestown, Ind. 



All specimens figured on the accompanying plate belong to the collection 

 of Mr. G. K. Greene. 



