Length from 2 to 3 lines ; width usually about one-fourth or one-fifth 

 greater than the length. The specimens are often much distorted, and 

 sometimes nearly circular ; but all the well-preserved individuals that have 

 come under my observation are transversely sub-elliptical, the width being- 

 greater than the length. 



This species differs from 0. chromatica, 0. Ida, and 0. desiderata, 

 in its proportions, and from the first of these particularly in having a thin 

 instead of a thick shell. In this latter character also it differs from 0. 

 nana (Meek and Hayden). On comparison of specimens, I cannot see 

 any difference between this species and one figured by Dr. Emmons in his 

 American Geology, PL I, fig. 10, the size, proportions, and surface char- 

 acters being precisely the same, so far as I can judge. The Virginian 

 species, as may be seen by Emmons' figure and also by specimens in my 

 possession, is (like ours) sometimes inequilateral. It occurs in Augusta 

 County, Virginia, in soft-whitish grey slates associated with graptolites. 



Locality and Formation. Our species occurs in the greenish and olive- 

 colored slates near the bridge of the Grand Trunk across the Chaudiere, 

 and also in similar slates, but of a darker color, at Cape Kouge, above 

 Quebec. These slates are interstratified with the Sillery sandstones, 

 which are at present classified as the upper part of the Quebec group, 

 but the question as to whether such is their true position or not, is 

 considered an open one. The only fossils found in the Sillery, up to the 

 present time, are this species and a small Lingula which will be described 

 as soon as good specimens can be procured. 



Collector. J. Richardson. 



OBOLELLA DESIDERATA. (N. sp.) 



Fig. 62, a, b. 



Description. Shell small, moderately convex. Ventral valve ovate ; 

 greatest width a little in front of the middle ; front angles and margin 

 uniformly rounded, the front margin sometimes with a portion in the 

 middle straightish ; the upper half slightly narrowed "towards the beak. 

 Dorsal valve nearly circular. 



Length and breadth from 3 to '4 lines. 



The specimens that have been collected are all, with the exception of 

 three or four, pressed quite flat. Those not distorted by pressure show a 

 moderate amount of convexity, the greatest elevation being at about one- 



