Maryland Geological Survey 157 



are close togetlier. On comparison it was found that the radiating striae 

 on tlie ]\Iai'vland specimens were finer tlian on specimens of this species 

 from the Hamilton shales of New York. This species is distinguished by 

 its strong convexit}-, semielliptical outline, deflected cardinal angles, and 

 finer, more numerous and more closely crowded striae than in C. mucro- 

 natus. 



Length. 10 mm.; width, 1"^ mm. Another specimen has the following 

 proportions : Length, 10 mm. ; width, 11 mm. 



Occurrence. — Eomney Formation, Hamilton Member. East bank 

 Evitts Creek below Wolfe Mill; McCoys Ferry; southwest of McCoys 

 Ferry; along Flintstone Creek in (!il])in; west of iron bridge over Town 

 Creek northeast of Oldtown ; on road about half way between Eomney and 

 Hanging Rock, W. V.a. 



Collections. — Maryland Geological Survey ; American ]\Iuseum of N'at- 

 ural History. 



Chonetes marylaxdicus n. sp. 



Plate XIII, Figs. l-(i 



Description. — Shell medium size, semielliptical, hinge-line as long or 

 slightly shorter than the greatest width of the shell. Ventral valve 

 gibl)ous, the central part having the greatest convexity, from which it 

 declines rapidly towards the front and is abruptly depressed towards the 

 lateral margins and cardinal angles, the latter being flattened. The bases 

 of at least three spines are shown on each side of the umbo, and the 

 spines are either straight or inclined laterally ; cardinal area rather nar- 

 row, hut Avider than that of the opposite valve. Dorsal valve moderately 

 concave, not equaling the convexity of the ventral valve. Surface of dorsal 

 valve marked by from 34 to 60 rounded or sometimes subangular striae 

 which increase by bifurcation and sometimes by intercalation, so that 

 there may be even a larger numljer on the ventral margin, and the striae 

 and interspaces are covered by very fine radiating, thread-like striae, while 

 well preserved surfaces show similar, closely arranged, thread-like con- 

 centric ones. Striae of ventral similar to those of dorsal valve. Interior 

 of ventral valve has a median ridge which extends from the beak for 



