Ili:i,i»i:i;i'.i i;<; I'm; \i \rii)\ i\ M \l;^ i.axd 9 



hinge-line produced beyond the body of llie shell into mucronate exten- 

 sions, hinge-line crenulate. 



" Surface of both valves nuu'ked by line, irregularly alternating, angular, 

 raised striae, which are not continuous over the umbo to the beak, and 

 wliich curve outward on tlie sides of the shell in passing to the margin, 

 the ciTrvature becoming stronger on approaching the hinge-line. The sur- 

 face is also marked by much finer, crowded, concentric lines, which con- 

 tinue to the beak. Oblique wrinkles along the cardinal margin are 

 present in many specimens. The interior of the valves, more especially 

 the pedicle, is covered with fine, closely crowded papillse, which gives to 

 the surface of internal casts a finely pitted or punctate appearance. These 

 internal papilhe may frequently be detected through the thin shell sub- 

 stance as dark spots, giving it a punctate appearance, but there are ap- 

 parently no perforations. The muscular impressions of the pedicle valve 

 are rather large and divergent and are free from impressions of papilla). 

 In the interior of the brachial valve a low median ridge reaches more than 

 half way to the front of the shell. 



"The dimensions of a medium-sized specimen are: Length, 28 mm.: 

 breadth, 30 mm.-' Weller, 1903. 



This species is the same as Stropheodonta hipartita which Weller de- 

 scribes from the Decker Ferry of New Jersey and which he considers the 

 same as the three shells described by Hall in Volume II of the Pale- 

 ontology of New York under the names Leptcena sp., Lepta'na hipariila. 

 and Stroplieodonta iextilis, all from the Coralline limestone of Schoharie, 

 N^ew York. It differs from the three forms described by Hall in having 

 the striae curve outwards on the sides of the shell in approaching the 

 margins, the curvature increasing towards the posterior portion of the 

 shell. This curvature is not mentioned in Hall's description and on ex- 

 amining the type material the strite do not curve but radiate from the beak 

 straight. While this form is the same as that described by Weller it may 

 prove to be a distinct species from Hall's. 



It is distinguished from S. plamilaia of the Lower Ilelderberg by the 

 curvature of the alternating angular striae, while the stria? of S. pJanidata 

 are fine and even. 



