22 



Cincinnati Society of Natural History. 



NEW SPECIES OF FOSSILS FROM THE HUDSON 

 . RIVER GROUP, AND REMARKS UPON OTHERS. 



By S. A. Miller and C. L. Faber. 



Orthodesma cylindricum, n. sp. 



Plate /, Fig. i, left side of a good specime?i; Fig. 2, left side of 

 another speci??ie?i ; Fig. 3, dorsal view of the same ; Fig. 4, 

 dorsal view of a smaller specimen somewhat injured. 



Shell above medium size, four to five times as long as wide ; 

 cardinal and basal lines posterior to the beaks, straight and 

 parallel to near the posterior end, which is obliquely rounded, 

 with the greatest extension at the postero-basal angle or limit 

 of the umbonal slope. Sides rounded posterior to the beaks 

 and very gently flattened toward the posterior end. Anterior 

 end gently contracted, forward of the beaks, and curved 

 slightly downward and rounded at the extremity. Beaks 

 small and extending beyond the cardinal line, so as to come 

 nearly in contact with each other, and terminating between 

 one-fourth and one-fifth of the length of the shell from the 

 anterior end. The umbones are compressed in all our speci- 

 mens. The sulcus below the umbonal ridge, that usually 

 forms a conspicuous character in this family of shells, is unde- 

 fined and scarcety to be distinguished in some specimens. 



Surface marked by concentric lines of growth, which are 

 strongest and best defined near the hinge of the shelL 



This species has some resemblance to O. curvatum and O. 

 rectum ; but it is much longer in proportion to its height than 

 either of them, and more uniformly rounded, beside being 

 wholly different from each of them anterior to the beaks. 



It occurs above the middle part of the Hudson River 

 Group, in Warren County, Ohio, and is in the collection of 

 both the authors of this article. 



