4« PALEONTOLOGY OF NEW-YORK. 



Sdrface marked by even rounded striss, which, at intervals, show small 

 tubular openings, while the intermediate space is minutely papillose or 

 punctate according to the condition of the surface. 



The specimen described has been a little compressed, but it appears to have 

 possessed a broad shallow sinus on the ventral valve, very similar to 0. ohlata 

 of the Lower Helderberg group : the stria) are stronger and more rounded than 

 in that species. 



The length of this specimen is nearly six-eighths of an inch, and its width 

 seven-eighths of an inch ; but it 48 probably not an. adult individual, and, without 

 more material, I hesitate to characterize it, since it belongs to a group of Orthides 

 of which there are numerous closely allied species. 



Geological formation and locality. 4n the Corniferous limestone of Western 

 New- York. 



Ortliis yanuxeiiii? . 



PLATE V. 

 Orthi* vanuxemi, Hall. See tho game under IlamiUon group. 



A single specimen of a ventral valve, from the limestone, possesses 

 characters undistinguishable from those of 0. vanicxemi. This specimen, 

 however, is the only one of the species which has come under my ob- 

 servation from the limestone. Numerous imperfect casts and exfoliated 

 shells bear close resemblance to the species, and may prove to belong to 

 the same. 



Geological formation and- locality. In the limestone of the Upper Helderberg 

 group, near Caledonia, Livingston county, N.Y. 



^ Ortliis seiiieic ( n. s.). 



PLATE V. 



Some imperfect specimens showing the interior of the ventral valve, 

 and also a small specimen of the ventral valve, possess characters ap- 

 proaching very nearly to O. vanuxemi. From the same locality there have 

 been obtained casts of a dorsal valve, which are more elevated in the 



