STANTON.] AKCIM3. 91 



Prof. W. F. Cummins and Dr. C. A. White some years ago obtained 

 large numbers of well preserved shells which I believe to belong to 

 this species. At any rate, the characters that are preserved in the 

 Coalville specimens agree in every particular with those from Texas, 

 figures of which are given for comparison. 



The species attains a considerably larger size than is indicated by 

 the dimensions above given. 



Locality and position. — Abundant near the base of the Cretaceous 

 section at Coalville, Utah, and occasionally found much higher in the 

 same section in the lower part of the "third ridge"; also in equivalent 

 strata at Bear Eiver city, Wyoming. The Texas specimens come from 

 the Timber Creek beds of Denton county, near the base of the Upper 

 Cretaceous section of that region. 



Genus NEMODON Conrad. 



Kemodon sulcatinus Evans & Shumard (sp.)? 



PI. xxt, Fig. 5. 



Area mleaUnd Evans & Shumafd, 1857. Trans. St. Louis Acad. Rei., vol. I, p. 39. 

 Xemodon sulcatinus Meek, 1876, U. S. Geol. Snr. Terr., vol. ix, p. 82, PI. 15, Yig. 6. 



Shell small, transversely elongate, ventricose, basal margin parallel 

 to the dorsal, nearly straight, but slightly sinuous in the middle; front 

 broadly rounded from the base to the hinge line, which it joins nearly 

 at a right angle; posterior end obliquely truncate, strongly sinuous 

 above the middle, and narrowly rounded into the base below; beaks 

 slightly in advance of the middle, prominent, incurved, and rather dis- 

 tant; posterior umbonal slope oblique, narrowly rounded. A narrow, 

 deep sulcus, almost at right angles to the hinge, runs from the beak to 

 the middle of the base. Surface of the casts with faint radiating stria 1 , 

 and the free margins crenate. A natural mold of the surface of the 

 shell shows about 25 tine radiating lines. 



Length, 6 mm ; height, 3 nnu ; convexity of one valve, about l.G mm . 



The specimens here described are a few small casts, the largest of 

 which is figured, collected by Mr. C. D. Walcott in the lower part of 

 his Upper Kanab valley Cretaceous section, where it is associated with 

 many species of the Colorado fauna. The types of the species came from 

 near Grand river, Dakota, and the only other reported locality is on the 

 Yellowstone river, 150 miles above its mouth, where it is associated with 

 species belonging to the Montana formation. The Kanab specimens 

 show slight differences when compared with those from the Yellowstone, 

 and it is possible that better material will show that they are really dis- 

 tinct; but the general resemblance is very close, and I think it best to 

 call them by the same name for the present. 



