No. 109.] 135 



Spirifer acuminatus, 



DcHhyris mcuminaius, Conrad : Annual Geological Report of Ne\v-York, 



1839, p. 65. 

 Spirifer cultrijugatus , F. Rgemer in Das Rheinische TJebergangsgebirge, 



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



This weil-marked and widely distributed American species has been 

 a-ecognized by M. de Verneuil, and Dr. Romer as identical with S. 

 cultrijugatus 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 ; biit I have not been able to find any published descriptiou 

 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 REMAINS OF THE HAMILTON GEOUP. 



Orthis vanuxemi ( n. s.). 



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

 line very short ; margins of the valves crenulated within ; 

 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 

 striae, which are perforate at intervals and increase both by 



