LAMELLIBRANCHIATA. 173 



In the volume of Plates and Explanations this species was referred to 

 L. Dckayi in the absence of the original specimen, which has since lieen 

 compared and found to belong to the Chemung group. 



Formation and locality. In a slaty sandstone of the Chemung group, eight 

 miles north of Binghamton, N. Y. 



Leiopteria linguiformis. n. sp. 



PLATE LXXXVUI, FKj. 23. 



Shell a1:)0ve medium size, erect, sub-rhomboidal ; body elongate-ovate, making 

 an angle of about 60° with the hinge-line ; length equal to three-fourths of 

 the height ; anterior margin nearly vertical from the byssal sinus to below 

 the middle of the valve ; basal margin broadly rounded ; post-basal margin 

 rapidly curving into the Aving. 



Left valve convex above, depressed-convex below. Right valve unknown. 



Hinge-line straight, nearly equal to the length of the shell. 



Beak acute, erect, prominent, rising above the hinge-line. Umbonal 

 region convex, subtending an acute angle. 



Ear small, triangular, bending slightly downward, limited by a well- 

 defined byssal depression ; margin nearly straight ; extremity rounded. 

 Byssal sinus shallow. Wing broad-triangular, joining the body below the 

 middle of the post-cardinal slope, not strongly limited ; margin concave ; 

 extremity acute. 



Surface marked by concentric stride which are strongly lamellose on the 

 ear, the pallial margins and on the wing. 



Ligamental area narrow, marked by two or three longitudinal grooves. 

 Muscular impression oval, situated near the middle of the post-cardinal 

 slope. 



The specimen described has a length of 33 mm., height 42 mm., and 

 hinge-line 32 mm. 



