12 PROCEEDINGS OF THE ACADEMY OF 



413.) The small shells thus identified have heretofore been regarded as the 

 young of M. occidentalism White and Whitfield, a species with which I formerly 

 identified the Michigan types of M. Whitfieldianus, a close comparison of speci- 

 mens, however, shows M. occidentalis to be quite destitute of the fine diverging 

 strife which belong to perfect specimens of the other species. M. occidentalis, 

 moreover, is more flattened between the umbonal ridge and the hinge-line, and 

 does not attain more than one-fifth the length of the other. It bears conside- 

 rable resemblance to Modiola lingualis, Phil., (Geol. Yorks. p. 209, pi. v. fig. 21.) 



ORTHONOTA, Conrad. 



Okthonota phaselia, n. sp. Shell transversely quadrangular. Beaks in- 

 conspicuous, nearly terminal, not raised above the slightly-curved hinge-line. 

 Ventral margin subparallel with dorsal, with a shallow sinuation in the middle. 

 Posterior end truncately curved, a little the most extended toward the dorsal 

 side; anterior end slightly produced below, with a deep lunette above. Shell 

 inflated from the anterior end to near the posterior. Greatest thickness a little 

 in front of the middle. Anterior muscular pit shallow, ovately pyriform. 

 Surface with a few remote concentric lines near the border. 



Length -35 (100) ; height -20 (57) ; thickness of both valves -13 (37). 



EDMONDIA, de Koninck. 



Edmondia nitida, n. sp. Shell small, equivalve, suborbicular, ventricose, 

 slightly oblique, with a subcentral beak. Hinge-line slightly extended poste- 

 riorly, obtusely rounded at the extremities ; anterior and posterior sides sub- 

 parallel ; ventral border circularly rounded, but a little produced in the line of 

 the umbonal ridge. Beak elevated above the hinge, obtuse, slightly incurved ; 

 umbonal ridge making an angle of 66 with the hinge-line; behind this ridge 

 the elope is abrupt to the posterior border; middle portion of the shell very 

 slightly flattened from the beak along the region anterior to the umbonal ridge. 

 Surface handsomely marked by rigid, regular concentric raised striae, with a 

 few remote, irregularly-distributed concentric furrows. The striation is pre- 

 served in all its sharpness to the very hinge-border. 



Length -59 (100) ; height -59 (100) ; thickness of both valves -30 (51). 



Closely resembles E. unioniformis, de Kon., (Anim. Foss., pi. i. fig. 4,) but 

 the latter is less finely and elegantly striated, and shows no flattening along the 

 region between the beaks and the ventral border. It is much less flattened 

 and less angular than E. binumbonata, Win., from Michigan. 



Edmondia nuptialis, n. sp. Shell of moderate size, transversely-suboval ; ia 

 adult specimens considerably inflated in the vicinity of the pallial border. 

 Beaks subcentral, small, incurred, somewhat elevated above the moderately 

 extended, slightly arcuate hinge-line. Ventral margin gently curved or nearly 

 straight in the middle; more rapidly curved toward the rounded, subequal ex- 

 tremities. Hinge structure obscure, but apparently consisting of one or more 

 lateral teeth on each side of the beak. Surface unequally and interruptedly 

 furrowed. Greatest thickness through the middle of the shell. 



Length -79 (100) ; height -62 (78) ; thickness of both valves -50 (63). 



This species is relatively larger than E. nitida, and is destitute of the obtuse 

 angulations descending along the anterior and posterior umbonal slopes of the 

 latter. An associated, if not identical, species is less ventricose, with less 

 central beaks, and can scarcely be distinguished from Lucina? retusa, Hall. 



Edmondia strigillata, n. sp. Shell rather small, rather gibbous, trans- 

 versely oval ; beaks subcentral, elevated, obtuse, somewhat strongly turned 

 forward. Ventral margin gently arcuate in the middle, more rapidly curved 

 toward the neatly-rounded extremities, of which the posterior is broadest. 

 Hinge-line curved, furnished with a pair of rather thick lateral teeth ; cardinal 

 ieetb, apparently none. Surface marked by fine radiating lines, and toward 

 the margin by a few irregular concentric wrinkles. 



[Jan . 



