310 Systematic Paleontology 



geniculate in front : dorsal valve forming an inclined plane from the hinge 

 towards the front, near which it is abruptly deflected, giving the valve a 

 deep concavity : hinge-line equal to the greatest width of the shell ; lateral 

 margins contracted, so as to leave small auricular extensions at the ex- 

 tremities of the cardinal border ; area sublinear, longitudinally striate : 

 interior distinctly granulose ; muscular attachments strongly marked." 

 Hall, 1857. 



Length 3.5 cm. ; width along hinge 5.6 cm. 



This is the Oriskany form of L. rhomhoidalis, with strongly marked 

 muscular scars. 



Occurrence. — Oriskany Formation, Eidgely Member. Cumberland, 

 Maryland ; Warren Point, Pennsylvania. 



Collection. — Maiyland Geological Survey. 



Genus LEPT.^N1SCA Beecher 

 LEPTiENISCA CONGAVA (Hall) 



Plate LVII, Figs. 2-5 

 Leptcena eoncava Hall, 1857, Tenth Ann. Rept. N. Y. State Cab. Nat. Hist., 



p. 47. 

 Leptwna eoncava Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 197, pi. xviil, 



fig. 2, 1861. 

 Leptanisca eoncava Beecher, 1890, Amer. Jour. Sci. (3), vol. xl, p. 238, pi. ix, 



figs. 1-5. 



Description. — " Shell • concavo-convex, hemispherical : ventral valve 

 regularly convex; umbonal region prominent; cardinal margin rounding 

 from the beak towards the lateral extremities: dorsal valve deeply con- 

 cave ; hinge-line less than the greatest width of the shell ; area of ventral 

 valve broad, that of dorsal valve linear; foramen triangular, nearly 

 closed by a thick callosity. Surface marked by very fine, close, radiating 

 strias, each fifth or sixth one a little more prominent than those between ; 

 crossed by fine regular concentric wrinkles, producing a beautiful sub- 

 cancellate appearance." Hall, 1857. 



Length 1.5 cm. to 3 cm.; width 1.7 cm. to 3.3 cm. 



This interesting brachiopod is common in a very restricted zone near 

 the base of the New Scotland in Albany County, New York. Occa- 

 sionally a single specimen is found higher in the same horizon. 



