418 PALAEONTOLOGY OF NEW YORK. 



specimens, figs. 50 and 51, are of the type of R. eximia, of small size. 

 Although there are few examples in the collection, tliey still show a 

 gradual increase in the plications, from those having the least to those with 

 the greatest number, without any possible means of drawing a line of sepa- 

 ration between them ; while among the New York specimens the separation 

 is comparatively easy. Considering these facts, the specimens are for the 

 present referred with some doubt to R. contractu, until more material can be 

 obtained, oflFering better means of comparison. 



Terebratula lincklseni vai . 



PLATE LX, FIGS. 32-37. 

 Compare T. TraversentU, Winch. Rep. on Grand traverse region, p 96. 1866. 



Among some Terebratuloid shells obtained from Thunder Bay, Michigan, 

 there are a few having some resemblance to T. linckleni, but differing in 

 some points which, if constant among a larger number of specimens, might 

 prove to be of specific importance in a group of shells of such close charac- 

 terg as Terebratula. These shells are usually more ventricose in the um- 

 bonal region than T. lincklczni, with a larger and more strongly incurved 

 beak, the perforation of which is also larger ; the front of the shell is likewise 

 much less gibbous, often being thin and somewhat flattened below the mid- 

 dle, and the greatest width being above the centre instead of below, as in 

 that species. Taking into consideration these points of dissimilarity, it 

 may be desirable to recognize it as a distinct variety until more material 

 may show its proper relations. 



Terebratula Ontario (n. s.). 



PLATE LX, FIGS. 45^8. 



Shell small, very broadly ovate or subcircular, with depressed convex 

 valves of nearly equal depth ; beak •'of the ventral valve incurved and 

 strongly truncated by a circular perforation, the lateral margin subcari- 

 nate. 



