52 PAL/EONTOLOGY OF NEW YORK. 



oz 



(if till' valvo, cxtt'iiiliiiji I'artluT toward iIk- posterior than toward tlu- 

 anterior inarfiin. 



Beak ol)tiisi'. rounded, central to tlie l)ody of the .<licll, (k-pressed, not 

 rishij; al)ove tlie liiiij:e-hne, nor extending to tin- hinge-margin; undional 

 region moderately convex, not delined laterally. 



Anterior ear small, narrow-triangular, not wi-U-di-dned ; extremity very 

 ohtuse, roundeil : margin slightly concave without a (k'ri(le<l hyssal sinus. 

 Posterior ear triangular, more than twice the length of the anterior, and defined 

 fnjm the nmhonal slope by the absence of the strong radii ; extremity acute- 

 angular; margin marked by a broad, rounded sinus. 



Test marked by about 40 strong, elevated rays, which aie somewhat 

 tiattened along their summits; usually alternating with one or two sharp or 

 rounded rays, crosseil by wry line, sharp, concentric stria?. The radii 

 gradually diminish in strength towards the ears, where they are represented 

 hy elevated, narrow lines. 



Litramental area inarkcil l>v several longitudinal strise. Other interim- 

 characters not known. 



The height of the specimen is ".17 mm., length 104 mm., liinge-liiu' 44 mm. 

 Three of the stronger rays occupy a space of 12 mm. at the liasal margin. 



The specimen described is thi' imprt'ssion of the exterior of a left valve; it is 

 quite characteristic and very distinct from other known species in its form and 

 surface markings. 



Ill ornamentation and general outlini' there is sonu' resemlilance lietween this 

 shell and L. macrodontus, but it is h'ss convex, the rays are more (4evate(l, and 

 more sharply defineil. The geological horizons of the two species are also 

 widely separated. 



Formation and localiti/. In coarse, arenaceous slates of the F])]ier Chemung 

 group, at Montrose, Suscpiehaiiua county, Peini. 



