ECHINODERMA TA—BLASTOIDEA . 48 3 



Kaskaskia of Kentucky, Tennessee, Alabama, Indiana, Illinois 

 and Missouri. 



16. P. sulcatus (Roemer). . Mississippic. 

 Calyx large, subglobose, with very short and obtuse base and 



truncate summit. Ambulacra and interradial areas very concave. 

 In size and shape much like P. cervinus but differs in its shorter 

 and more obtuse base and less angularly expanding ambulacra. 

 Kaskaskia of Illinois and Missouri. 



17. P. cervinus Hall. (Fig. 1794.) Mississippic. 

 Basal plates forming a pentagonal cup with elevated angles and 



concave sides. 



Kaskaskia of Alabama and Illinois. 



VII. El^acrinus Roemer. (Nucleocrinus Conrad.) 



Calyx olive-shaped, usually smaller toward the base. Base 

 usually excavated. Basals small, inconspicuous, sometimes hidden 

 within the stem cavity. Radials small, with very short limbs. 

 Deltoids greatly enlarged and elongated, forming over two thirds 

 of the entire calyx, the posterior one wider than the others and 

 divided by a large anal plate. Ambulacra almost entirely enclosed 

 by the deltoids. Lancet plates exceedingly long and narrow, partly 



Fig, 1795. Elceacrinus verneuili, 4 views of a typical specimen, (After 

 Troost and E, Wood, ) 



exposed. Side plates numerous. Hydrospires two on each side 

 of an ambulacrum. Spiracles ten, in five pairs, notching the upper 

 ends of the deltoids. Anal opening distinct. Summit covered 

 by comparatively large orals arranged nonsymmetrically and form- 

 ing a flattened disc which completely closes the mouth opening. 

 Column round or somewhat five-sided. Devonic. 



