OF DEXISON UNIVERSIIV. -^9 



lUiijiiconella cuntntcta, H. 

 (Plate X, Fig. 9.) 



We are quite unable to distinguish any diflerences between a 

 small species with very acute plicae and that described by Prof. Hall, 

 from the Chemung. Prof. Hall himself made the same identification 

 in 1867, and as the nauie was applied in 1843, it ranks any other name 

 in vogue for the same shell. The range of individual variation is as 

 great as in thai rjuoted. The species is rare in the free stone of mid- 

 dle Waverly. 



In a i;enus is conservitive as this one a i^reater vertical range of 

 species is t'^ be expected th m in many orher groups. 



ElnjnchoneJla siibcunrata, U? 

 (Plate VII, Fig. 2-^.) 



A small species from just above conglomerate I. has nearly the 

 form of the species quoted. The sandy matri.\ makes a careful study 

 impossible. Our specimen is smaller and less broad than Hall's types, 

 but it is not easy to !)oint out specific distinctions, the static character 

 of the genus makes the continuance of a species during the in'.-rv il 

 between the horizon in question and that of the Warsaw possible 



Rhijnchonella sageridim, ^Vin. 



(Perhaps a variety of R. sa|)pho, H ) 



Shell rather gibbous, thickness ecjual to more than one-third the 

 width, transversely extended ; ventral valve broadly oval to slightly 

 pentagonal, with a pointed incurved beak; mesial sinus rather dis- 

 tinct, narrower than one-third the width, extending less than half way 

 to the beak, with three to four strong plica: ; lateral surfaces convex, 

 with five or six plicae on either side, which rather rounded above; lat- 

 eral margins nearly straight, meeting the beak at an angle of about 

 110°; length of lateral margins greater than half the length of the 

 valves, intersecting the evenly-curved ventral margin at a pomt in 



