New Species of Paleozoic Fossils. 200« 



SUPPLEMENT. 



The species of Pentamerus, cited on page 197 as P. galeaius, proves, on an exam- 

 ination of specimens, to b3 a distinct form, occurring at a horizon below the known 

 limits of that species; and may be described as follows : 



Pentamerus nucleus n. sp. 



Shell small, subglobose, with strongly inflated ventral umbo; width a little 

 greater than the length. Ventral valve much the larger ; very ventricose ; cardinal 

 margins rounded, from the body of the valve to the border of the somswhat small 

 foramen ; middle of the valve elevated, forming a fold. Dorsal valve transversely 

 elliptical, strongly convex, umbo somewhat inflated; the middle of the valve 

 depressed, forming a strong sinus ; cardinal border rounded, leaving the beak promi- 

 nent above the line and strongly incurved beneath the opposite ventral beak. 



Surface marked by comparatively strong angular plications, about seven on the 

 dorsal valve and six on the ventral. Two of these, depressed on the dorsal and 

 elevated on the ventral side, form the mesial fold and sinus. 



This species somewhat resembles small individuals of P. galeatus, and seems to be 

 intermediate between that and P. fornicatus of the Clinton group of New York. v 



Formation and locality. — In limestone of the. Clinton group, near Louisville, 

 Kentucky. From the collection of Dr. Knapp. 



