TEREBRATULID^ OF THE HAMILTON SHALES. 389 



Young specimens, which I refer to this species, are more gibbous than 

 the older ones: The larger specimens are from six-eighths to seven- 

 eighths of an inch long and five-eighths of an inch wide. 



This species is proportionally wider and with more extended beak than the 

 T. sullivanti, and more regularly arcuate from beak to base of the ventral valve : 

 it is, moreover, not emarginate in front. It appears to be a well-marked species, 

 and, in its larger individuals, will be readily distinguished. 



Geological fonnation and localities. From the limestone of the Falls of the 

 Ohio (sent to me by Dr. jAiiES Knapi* of Louisville, Kentucky) ; and also from 

 the Coniiferous limestone of f anada West : collected by Mr. De Cew. 



Terebratula rfleiiiingeii. 



PLATE LX. . 



Terebratula ramingeri : Hall, Sixteenth Report on the State Cabinet, p. 48. 18G3. 



Shell ovate, more or less gibbous, truncate or slightly sinuate in front. 

 Ventral valve gibbous above the middle ; umbo gibbous, inflated ; beak 



prominent, incurved over the opposite beak, and truncated by a round 



foramen which is often mainly anterior to the . apex, and completed 



on the lower side by two deltidial plates : cardinal slopes rounded, 



often depressed in the middle towards the front. 

 DoRPAL valve extremely gibbous, little longer than wide; the greatest 



convexity at the middle or above. 

 Surface marked by fine concentric striae which are often crowded into 



prominent wrinkles towards the front. Shell-structure finely punctate. 



The interior shows a short terebratuliform loop, which is abruptly 

 recurved at its lower extremities. 



This species was first indicated from specimens sent by Dr. E(EMINGer, from 

 Thunder bay, Michigan ; but it has since proved of common occurrence in New, 

 York. The Michigan specimens are usually more gibbous and distinctly depressed 

 or sinuate in front ; while that charactci-, though present in some of the eastern 

 specimens, is not constant. There is, however, no difficulty in recognizing the 

 characters of the species in any well-preserved specimens. 



This species is the smallest of the genus, or of the family, knoAvn as occurring 

 in the Hamilton shales of New- York. 



