BRACHIOPODS. 61 



back under the braehial processes, one on each side of a well- 

 defined rounded ridge, that becomes suddenly smaller between 

 the anterior pair ; cardinal process rhombic, subconical, mod- 

 erately prominent, and having its posterior side marked by 

 deeply impressed divaricating striae ; sockets well defined ; 

 braehial process rather strong, and directed obliquely forward 

 and laterally ; internal surface, excepting the radiately striated 

 front and lateral margins, nearly smooth. 



Ventral valve a little convex at the umbo, and flat or slightly 

 concave between the umbo and the front and lateral margins, 

 but sometimes having a low, very obscure mesial elevation 

 toward the front ; beak small and very short, or scarcely 

 equaling that of the other valve, arched at the apex, but not 

 strongly incurved; area about twice as high as that of the 

 other valve ; well-defined, tapering rather rapidly toward the 

 lateral extremities, arched with the beak and directed back- 

 ward and downward at decidedly less than a right angle to 

 that of the other valve ; foramen broad-triangular, and partly 

 occupied by the cardinal process of the other valve. Interior 

 with muscular scars occupying a rather deep bilobate impres- 

 sion, extending nearly or quite to the middle of the valve, and 

 usually defined by a low ridge most distinct on each side ; scars 

 of adductor muscles small, separated by a mere trace of a 

 raised line ; those of the divaricator muscles of moderate size, 

 longitudinally striated, and having their narrow posterior ends 

 extending backward nearly to a small triangular, transversely 

 striated space occupying the interior of the beak ; those of the 

 ventral adjuster muscles smaller and shorter than the divari- 

 cators, and situated nearly under the hinge teeth, which are 

 moderately prominent, sub-trigonal and oblique ; vascular 

 markings with their lateral divisions curving up backward and 

 sending off several branches, while the other divisions extend 

 forward and bifurcate so as to occupy the anterior region ; 

 anterior and lateral margins crenate within by very short 

 striae. 



Surface of both valves ornamented by moderately stout, 

 radiating striae, the posterior lateral of which curve so strongly 



