562 GEOLOGY OF OHIO. 



are referred to the C. undulostriata of Hall (Plate 37, Fig. 9 C.) from the 

 Niagara shale at Lockport, New York. The'valves are subovate, strongly 

 convex, especially along the umbonal ridge. The basal margin is moderately 

 convex. Both extremities are rounded. The beak has a positionnear the 

 anterior end of the shell alongf the hinge line. The posterior side is 

 very moderately convex, and makes a general angle of about 135 degrees 

 with the hinge line. The hinge line is moderately inclined. The sur- 

 face is marked by distinct though rather distant concentric striae, between 

 which occur much finer and more numerous striae of growth, seen only 

 tinder a lense. 



The specimen from Brown's Quarry is 6.2 mm. long, and 3.8 mm. 

 high. The depth of the valve is about 1.2 mm. Of large concentric 

 striae there are five, not counting those within a millimeter and a half 

 of the beak. (Plate 37, Fig. 9 a.) The Soldiers' Home specimen was 7.5 

 mm. long, and 4.3 mm. high. The depth of the valve was 1.3 mm. 

 (Plate &7, Fig. 9 b.) 



Tellinomya elliptica, Hall. 



i (Plate 37, Figs. 4 a, b, e.) 



In the collection of Dr. Charles Welch, of Wilmhgtonisavalve ob- 

 tained at Todd's Fork by his father. As regards identity with knowhspe- 

 cies the choice lies between T. elliptica of the Clinton (Plate 37, Fig. 10) and 

 T. cequilatera of the Coralline Limestone (Plate 37, Figs. 4d, e, f). With 

 only the published figures to serve as guide the first species is* a little 

 larger and has a more rounded posterior extremity, but the beak is sim- 

 ilarly located. The second species has nearly twice the size. So that the 

 Todd's Fork specimen seems to more nearly agree with tellinomya 

 elliptica. 



The Todd's Fork specimen is 33 mm. long and 21 mm. high. The 

 lower outline is equally convex. The upper outline is rather straight 

 from the beak for some distance towards either extremity. The anterior 

 extremity is more rounded than the posterior one. From a line drawn 

 vertically through the beak the anterior extremity of the valve lies 13.5 

 mm. and the posterior 19 mm. The shell is quite regularly convex. A 

 sort of rounded ridge extends from the beak backwards and a similar 

 one forwards, marking off a posterior and an anterior lunule. Con- 

 centric striae are rather indistinct and not regular in disposition. No 

 teeth were found and hence the generic reference of this shell is not 

 certain. 



