174 PALAEONTOLOGY OP N^VV-YORK. 



Productella laclir}mosa, var. lima. 



PLATE XXV. 



Slrophamena lima : Comead, Jour. Acad. Nat. Sciences, Philadelphia, Vol. viii, p. 256. 



This species is described by Mr. Conrad as follows : 

 " Semiorbicular ; lower valve ventricose, depressed in the middle, most 

 " profound towards the base ; surface with numerous elliptical tubercles 

 " disposed somewhat in quincunx order ; umbo ventricose ; superior 

 " lateral spaces much depressed. Locality : Occurs with the preceding 

 " species [ i. e. P. lachrymosa, at Chemung-narrows]. Differs from the 

 " last in the depressed middle, much more numerous shorter tubercles, 

 " etc. The size is nearly the same." 



Among the collections, and associated with P. lachrymosa, are specimens cor- 

 responding with this description; but I find so many intermediate forms, that 

 with my present sources of information I cannot regard them as of a distinct spe- 

 cies. Characteristic specimens of these are figured in connexion with P. lachry- 

 mosa. The well-marked specimens are distinctly depressed in the middle, giving 

 the front a sinuate aspect ; while the dorsal valves present a corresponding ele- 

 vation ; the latter showing as a depression in impressions of the interior of the 

 valves, which are often the only condition in which we have them. 



In these characters the shell approaches P. boydii; but the ventral valve is 

 usually more gibbous, the depression is much broader and becomes obsolete, 

 while the character of the spiniferous tubercles is very distinctive. 



Geological formation and localities. In the Chemung group, associated with P. 

 lachrymosa, at Randolph and South-valley in Cattaraugus county ; Ellington in 

 Chautauqua county, and other places. 



Prodnctella lacliryiiiosa, var: sti^iiata. 



PLATE XXV. 



Shell subovoid or hemispheric. 



Ventbal valve ventricose, regularly rounded on the surface, sometimes 

 nearly flat towards the front ; hinge-line less than the width of the 

 shell ; umbo rounded and much elevated above the hinge-line ; apex 

 closely incurved. 



