LAMELLIBRANCHIATA. 45 



smaller intermediate implanted rays, crossed by fine, regular, elevated sharp 

 lines of growth, which at intervals are raised into lamellas, and appear in the 

 cast as strong transverse ridges crossing the radii. The turrows between the 

 radii are narrower than the rays. The regular alternation of the radiating 

 lines where seen is a very conspicuous feature. The right valve is marked 

 })>• more numerous and subdued rays, and their alternation is somewhat 

 obscure. The ears show fine radiating lines and stronger and more crowded 

 concentric striae. 



The differences between the right and left valves, are the convexity, the 

 surface markings, and the deep byssal sinus of the right valve. 



The characters of the interior are not known. 



A medium-sized individual has a height of 47 mm., longitudinal diameter 

 54 mm., hinge-line 32 mm. A smaller specimen measures in height 35 mm., 

 length 38 mm., hinge-line 24 mm. 



The lai'gest specimen (imperfect) shows a height of 74 mm., and a length 

 of 88 mm. 



In outline and general aspect this species closely resembles L. macrodontus 

 (plate 8, figs. 9, 10), but differs in the obliquity of the beak, wider anterior 

 ears, and more elevated and numerous rays. It differs from L. magnijicus in 

 its outline, larger anterior ears, longer hinge-line, and finer radii of the ears. 



The anterior ears of this species, and also of L. solox and L. polydorus, are 

 smaller than in the species referred to Aviculopecten. 



The specimens mostly preserve both valves in connection. A large specimen 

 (plate 82, fig. 5), occurring in the harder argillaceous sandstone, attains nearly 

 the dimensions of L. cymbahn (plate 24, fig. 8), but difliers conspicuously in the 

 more numerous, strong radii, their gentle curvature toward the anterior side, 

 and the smaller area of surface upon the anterior side of the vertical axis of 

 the valve. 



Formation and locality. In the shales of the Hamilton group, Fultonham, 

 Schoharie county, N. Y. 



