No. 109.] 135 



SriRIFER ACUMINATUS, 



Ddthyris <acuminattis, Conrad : Annual Geological Report of New-York, 



1839, p. 65. 



Spirifer culirijuffatuf, F. R<EMEa in Das Rheinische Uebergangsgebirge, 



1844, pa. 70, pi. iv, f: 4 a, b. c. 



This well-marked and widtily di.stributed American species has beea 

 recognized by M. de Verneuil and Dr. Romer as identical with S, 

 <ultrijugaf.us of Europe. The species was, however, described by Mr. 

 Conrad five years before the European one. 



This species was designated by the late Prof. A. Eaton as Spirifer 

 alternatus ; but I have not been able to find any published descriptioa 

 of it. 



It occurs in the Upper Helderberg limestone, throughout, in New- York 

 and Ohio, and in Indiana and Kentucky in the continuation of the same 

 beds. It likewise occurs in the Hamilton group ( See Spirifer prora). 



ORGANIC REMAIXS OF THE HAMILTON GROUP. 



Orthis vanuxemi ( n. s.). 



Shell circular or transversely a little oval, compressed; hinge- 

 line very short ; margins of the valves crenulated within j 

 interior minutely punctate : dorsal valve depressed-convex; 

 beak scarcely distinct from the cardinal border, not incurved ; 

 teeth and dental process prominent : ventral valve nearly flat, 

 or a little concave towards the front, slightly convex in the 

 umbonal region ; beak small, extending little beyond that of the 

 other valve, arched but not incurved ; area very small, scarcely 

 equalling more than one third the greatest breadth of the shell, 

 arcuate; foramen comparatively large, triangular, and partly 

 filled by the dental process of the other valve ; teeth prominent. 

 Surface ornamented by fine, closely arranged, radiating tubular 

 strise, which are perforate at intervals and increase both by 



