MIOCENE MOLLUSCA AND CRUSTACEA. 63 



men. The species, however, can not be a true Mysia, as it has a broad pos- 

 terior hinge plate, a thickened shell, and much larger muscular scars than 

 exist in shells of that genus. It appears to me to be much nearer the true 

 Lueinae. 



The shell, so far as can be ascertained from the fragment, is circular in 

 outline, or nearly so; only moderately convex and much thickened in sub- 

 stance; outer surface with thickly crowded, lamellose, concentric lines, and 

 a posterior sulcus moderately well marked. In the interior the hinge plate 

 is wide behind the beak, and the posterior lateral tooth obsolete: muscular 

 scar on the posterior side moderately large, and bordered by a deep sulca- 

 tion corresponding to the sulcus on the exterior. 



Locality: The specimen is among the shells from Shiloh, N. J.; and 

 belongs to the collections of the National Museum at Washington, D. C. 



LUCINA CKENULATA. 



Plate x, tigs. 7-15. 



Lucina erenulata Conrad; Miocene Foss., p. 39, PI. xx, fig. 2; Proc. Acad. Nat. Sci. 



Phil., 1862, p. 577; Meek, Check List, p. 8; Tuoiney and Holmes, Plioc. Foss. 



S. C, p. 60, PI. xvin, tig. 14; Heilpriu, Proc. Acad. Nat. Sci. Phil., 188?, p. 403. 

 Compare L. Jens H. C. Lea: Trans. Am. Phil. Soc, vol. 9, p. 14, PI. xxxiv, fig. 19. 



" Shell lenticular, with numerous concentric laminae; a submarginal 

 fold on the posterior side; posterior extremity truncated; cardinal line 

 straight, oblique; beaks central; cardinal and lateral teeth distinct; margin 

 minutely crenulated." (Conrad.) 



The larger individuals of this species which I have seen from the 

 Miocene beds of New Jersev do not exceed one-fourth of an inch in diam- 

 eter. The shell is subcircular in outline, moderately ventricose and deeply 

 excavated in front of the small, pointed and subcentral beaks. The surface 

 of the valves is strongly lamellose with faint radiating striae, corresponding 

 to the crenulations on the inner margins of the shell. The features of the 

 interior are distinct, especially the lateral teeth, which are proportionally 

 strongly developed, and the muscular scars very well marked. In very 

 many of the shells the radiating striae are distinctly marked on the interior 

 of the valves. 



