M.\i{Yr,A\i) (iKoi,(i(ii'' \i. siu\i;v 177 



iii;^' I'min iiiiiliiiiK's to |i()s|ci'iiir l),-i>;il iii;i iLii ii : liimiles (Ic'Oply (IcprC'SScd; 

 iintci'iiir side \\\<j:\\ slidiiltlcicd. iniiiuletl; posterior hi<,di shouldcrod, angu- 

 laU'tl; iiiiii^uiii crciiidaliMl." ('Im-k, ISIHl. 



Length, H iiiiii.; widlh. ', .'> inin. 



Occurrence. — Nanji:.mov I'okm aiion. W rst of I'oit Tobacco, ^ mile 

 below C'ha|)('l I'oiiil. WOodsloek. 



Cnllci'lioiis. — loliiis ilopkiiis I'liivei-sily. ^^al•_vlalld Geolo<,nciil Sui'vey. 



LUCINA sp. 



A single fragment, evidently of a large Lucina, was round, which is 

 very different from any other form known from Maryland or Virginia. 

 It probably belongs to a new species of Lucina, or to L. claihoriiensis 

 Con.; but our only specimen is too imperfect to determine. The shell is 

 fragile, moderately thin, and the valves very shallow. It has abont 

 forty, nigose, concentric lamellae with faint, wavy, radiating lines be- 

 tween them. Hinge, scars, and pallial line are imknnwn. Length and 

 height abont 30 mm. 



Occurrence. — jSTaxjejeoy Foematiox. Popes Creek. 



Collection. — Maryland Geological Survey. 



Family CARDITIDAE. 



Genus VENERICARDIA Lamarck. 



This genus is very abundantly represented in the Maryland Tertiary 

 and especially in the Eocene. The Eocene forms are very numerous and 

 range throughout the entire horizontal and vertical extent of the forma- 

 tions. The variation in form is very great and has led to the establish- 

 ment of several species and varieties, all of which have been referred, 

 by most later authors to V. planicosta. Three forms, possessing con- 

 stant differences, may be recognized, and as these are each definitely 

 restricted in stratigraphic range, and are hence of geologic value, they 

 are given names. 



Eogers ' described from Virginia a species of Venericardia which he 

 called y. ascia. As this form has never been recognized, from Mary- 



1 Trans. Amer. Philos. Soc, vol. vi, 1839, p. 374, pi. 29, Us. 2. 

 12 



