Hambach — Revision of the Blastoideae. 



53 



Pentremites obtusus n. s. 



Fig. 13. 



Among the great number of Pentremites {Pentremites co- 

 noideus) so characteristic of the Boonville locality, we find by 

 close examination of a large amount of material that they are 

 not all one and the same kind and we can 

 readily pick out a number which, although re- 

 sembling very much Pentremites conoideus, differ 

 constantly in certain characters from this spe- 

 cies, so that we are forced to regard them as a 

 distinct species. Their body isconical with aflat 

 basal portion, the small basal pieces not visible in a side view; 

 ambulacrum narrow with a rounded surface and extending to 

 the base of the body. Vertical diameter never, even in a 

 small specimen, greater than the horizontal one, by which it 

 can easily be recognized from P. conoideus. Interambu- 

 lacral space smooth and not as much depressed as we find it 

 in Pentremites conoideus. Genital openings small and close 

 together. It is a distinct Warsaw species. 



Geological position and locality : It occurs in the Warsaw 

 limestone of Boonville, Missouri. 



Fig. 13. 



Pentremites angustus n. s. 



Fig. 14. 



Body elongate, obtuse, conical. Base small, flat and not 

 visible in a side view. Ambulacrea as long as the whole 

 body and nearly three-sixteenths of an inch in width, extend- 

 ing a little above the fork piece sinus and slightly rounded on 

 the surface. Poral 



f 



openings twelve to one- 

 eighth of an inch. 

 Interambulacral space 

 smooth and not de- 

 pressed in the center. 

 Lateral expansion of 

 the deltoid externally 

 visible and occupying 

 fully one-half of the 



a. Pentremites angustus. 



b. " " base view. 



c. Pentremites conoideus, base view. 



