BRACHIOPODA. 235 



shell. Beak broad, rounded, but little incurved. Crenulations on hinge line obscure. 

 Cardinal extremities obtuse. 



Surface marked with numerous, fine, rounded, radiating, bifurcating costae, which 

 are separated by broader, flatter interspaces; in the middle of the shell 2 costae occupy 

 the space of 1 mm. An exfoliated portion of the shell shows the elongate-oval adductor 

 muscle impressions, and the large, plicated fan-shaped diductor muscular markings. 



Hall describes the brachial valve as follows: "Dorsal valve (of this species) deeply 

 concave, radiatingly striated, the striae finer than those of the ventral valve. The in- 

 terior of the valve is marked by well-defined muscular areas; and outside of these the 

 vascular and ovarian spaces occupy a large part of the shell, having a well-defined semi- 

 elliptical area of a width little greater than the length, and somewhat contracted at the 

 cardinal angles. The margin outside of the vascular area is striate-punctate." — Hall, 

 1859. 



Remarks — One complete pedicle valve and three imperfect- ones have come under 

 my observation. None of the specimens show the elongated hinge line which character- 

 izes some of the New York specimens. Swartz says: "Stropheodonla magnivcntra is 

 easily distinguished from all associated Stropheodonta by its external ornamentation, 

 i. e., by the few widely separated obscure striae on the ventral valve, and by the very 

 delicate and exceedingly numerous striae of the dorsal valve. Another feature is the very 

 high ventral cardinal area." — Swartz, 1913. 



Horizon — Lower and upper beds. 



Figured specimens No. 27473 Walker Museum. 



Genus Brachyprion Shaler 



Brachy prion cf. majus Clarke 



Plate 62, figures 6. 7. 



1874. Strophomena inequiradiata Billings, Pal. Fossils, vol. 2, pt. 1, p. 24 (not fig. 13), 



pl. 2, fig. 4. 

 1900. Brachyprion majus Clarke, Mem. N. Y. State Mus., vol. 3, p. 54, pl. 8, figs. 



8-13. 

 1908. Brachyprion majus Clarke, Mem. N. Y. State Mus., vol. 9, pt. 1, p. 190, pl. 36, 

 figs. 1-6. 



Description — Shell of medium size, semi-circular to semi-elliptical in outline; 

 length greater than width. The dimensions of the separate brachial and pedicle valves 

 of different individuals are: Length 20 mm., width 28 mm., and length 16 mm., width 

 22 mm. The hinge line equals the greatest width of the shell, and is finely denticulate 

 for about half its length. 



Pedicle valve moderately convex, umbonal region broad and sloping abruptly to 

 the posterior margin. Beak slightly elevated, flattened and incurved over the hing«. 

 line. Cardinal extremities sharply defined. 



An interior of the brachial valve shows the valve to be moderately concave with 

 a well defined mesial sinus which broadens a little toward the anterior margin. The 

 surface exhibits a regularly marked pustulose character. 



Surface of both valves marked by fine, radiating, irregular costae. These vary in 

 size and increase by interstitial addition and by bifurcation, producing a fasciculate 

 appearance. These are crossed by fine, concentric markings which have been poorly 

 preserved in the specimens observed. 



Remarks — The species is sparingly represented by one doubtful pedicle valve, and 

 the internal casts of a few brachial valves. The form bears a stronger resemblance to 

 Brachyprion majus Clarke of the Grand Greve limestone, Quebec, Canada, than to the 

 same species in the Oriskany of Becraft mountain, New York. In the apparently mature 

 forms the irregularity of the surface markings still persists giving the fasciculate appear- 



