MIOCENE MOLLUSCA AND CRU STACEA. 93 



Saxicava bilineata. 

 Plate xvi, figs. 1-3. 



Saxicava bilineata Con.: Miocene Foss., p. 18, PI. x, fig. 4; Cat. Proc. Acad. Nat. Sci. 



Phil., 1862, p. 571; Meek, Check List, p. 12. 

 S. arctica (Linn.) and 8. bicristata (Sandb.) Otto Meyer: Proc. Acad. Nat. Sci. Phil., 



1884, pp. 108 and 109. 

 8. arctica Linn, var bicristata Conrad (error for Sandbergerf) O. Meyer: Proc. Am. 



Phil. Soc, 1888, p. 137. 



" Shell irregular in form; lines of growth profound; posterior side bicar- 

 inated, the intervening space being a slightly concave furrow; posterior 

 extremity direct, emarginate; right valve with two small diverging teeth." 

 (Conrad.) 



I have seen but few specimens of this shell, and those single valves 

 only, except one very young individual. The general form would appear 

 to be an oblong or trapezoid, with parallel dorsal and basal margins; but 

 from this they deviate in almost every direction. The anterior end is short 

 and the posterior narrow or wide, and the body of the shell extremely 

 variable, the only constant feature which I have seen being the two ear- 

 inse of the posterior cardinal margin; these are distinct and angular, with 

 the intermediate space concave, and the crests of the carinae subnodose or 

 subspinose in many cases, though in others they are only roughened by the 

 concentric lines where they cross. A single strong curved tooth and a deep 

 pit is present in each valve. I have not seen them with the "two small 

 diverging teeth" in the right valve. 



Locality: In the marls at Shiloh and at Jericho, N. J. 



