812 NORTH AMERICAN INDEX FOSSILS. 



Muscle scar horseshoe-shaped, open in front, in the form of a 

 strong band on the left and a weak or broken line on the right 

 (see Figs. 1195 and 1196, c). Surface smooth, sometimes with a 



,- V: 



Fig. 1 195. Anisomyon alveolus, top and side view. (After Meek.) 



few coarse plications, more rarely finely striate. Jurassic-Cretacic. 



658. A. meeki Gabb. Comanchic-Cretacic. 

 Elliptical, apex nearly centren, strongly pointed and curved, sur- 

 face flat, with faint, concentric undulations. 



Horsetown of California; Nanaimo of Vancouver. 



659. A. centrale Meek. Cretacic. 

 Broader than the preceding, more nearly circular ; slopes, except 



anterior one, nearly straight. Surface with fine radiating striae 

 and a few, coarse, radiating grooves. 



Colorado formation of New Mexico and Colorado; also in west- 

 ern Canada. 



660. A. alveolus (M. and H.). (Fig. 1195.) Cretacic. 



Fig. 1 1 96. Anisomyon patelliformis ; a, b, side and front view of a specimen; c, 

 top view of the type specimen. (After Meek. ) 



Elliptical, beak excentric ; surface slopes very gently convex. 



Pierre of Yellowstone, Black Hills and Canada. 

 661. A. patelliformis Meek and Hayden. (Figs. 1196-1197.) 



Cretacic. 



Subovate, broadest posteriorly, high, with beak rather sharp, 

 slopes irregularly convex. 



Pierre of Nebraska, Yellowstone and Black Hills. 



