12(3 UNITED STATES CxEOLOGIGAL SURVEY OF THE TERRITORIES. 



A. laticosta, Deshayes, is certainly not an Astartc, as it has distinct lateral teeth.* 

 Dr. Stoliczka has also figured a somewhat similar species, from the Creta- 

 ceous rocks of India, under the name Gouldia trigonoides ; but it departs 

 .'still more widely from our shell in its less rounded form and larger and less 

 numerous concentric costa?, and also differs in having its free margins 

 crenate within. Judging from Dr. Stoliczka's fig. 4, pi, x (vol. Ill, Palaeont. 

 Indica), there would seem to be reason for believing that his species, like 

 ours, has a posterior marginal furrow for the reception of a posterior lateral 

 tooth. It is probable that most of the Cretaceous species described under 

 the name Astarte belong to Eriphyla, Gouldia, and perhaps several other 

 allied genera. 



Locality and position. — Yellowstone River, 150 miles above its mouth; 

 from the upper part of the Fort Pierre group of the Upper Missouri Creta- 

 ceous series. 



SOLEMYID.^. 



Genus SOLEMYA, Lamarck. 



Synon— Solemya, Lam. (1818), Hist., V, 488; ib., 2e eU, VI, 123.— Feruss. (1821), Tab. Syst , xliv.— G. B. 



Sowerby (1822), Gen. Sh., fasc. 7.— Blaiuv. (1827), Diet. Sci. Nat., XLIX, 422.— 



Menke (1828), Syn. ; and (1830), ib., 2e 6d., 119.— Desh. (1830), Encyc. Me"th., Ill, tab. ; 



and (1832), ib., 956— Roemer (1839), Verst. Ool. Nacbtr., 42.— Gray (1842), Synon. 



Brit. Mas., 91; and (1847), Proceed. Zool. Soc, 192.— H. and A. Adams (1S57), Gen. 



Recent Moll., II, 482.— Meek (1873), Palajout. Obio, I, 206. 

 Sohnimya (Bowdicb), G. B. Sowerby (1822), Geu. Shells, fasc. 7 ; and (1842), C'oncb. Man., 2d 



ed., 262. 

 Solenomya, Leacb (1823), Synon. Brit. Mns., 58. — Herrmannsen (1849), Indicia Gen. Malac, II, 



481.— Meek and Worthen. (1866), Paheout. Illinois, II, 349, aid ib. V, pi. 27. 

 Solenymya, Swainson (1840), Malac, 366. 

 Uaneia, King (1850), Permian Fossils of England, 177. 



Etym. — Solen and Mya ; from a fancied resemblauce to these two genera. 

 Type. — S. australie, Lam. 



Shell transversely elongate-oblong, equivalve. inequilateral, very thin, 

 rounded and gaping at the ends; surface smooth, or showing obscure radiat- 

 ing marks, and covered with a polished, corneous, brownish epidermis that 

 projects beyond the free margins; beaks depressed to the horizon of the dorsal 

 margin, and located posteriorly; hinge with an obscure cardinal tooth in each 

 valve, and an oblique, posterior, internal process or fulcrum for the support 

 of the ligament, which is partly internal and partly external ; pallial line 

 simple; anterior muscular impression shallow, broad oval-subquadrate; poste- 

 rior smaller and ovate. 



• It should be remembered that iu first proposing the genus Astarte, Sowerby distinctly mentions 

 llir recenl .1. Scoti$a, which lias no lateral teeth, as the typical species. 



