MIOCENE MOLLUSCA AND CRU STACEA. 93 
SAXICAVA BILINEATA. 
Plate xvI, figs. 1-3. 
Saxicava bilineata Con.: Miocene Foss., p. 18, Pl. x, fig. 4; Cat. Proc. Acad. Nat. Sci. 
Phil., 1862, p. 571; Meek, Check List, p. 12. 
S. arctica (Linn.) and 8S. bieristata (Sandb.) Otto Meyer: Proc. Acad. Nat. Sci. Phil., 
1884, pp. 108 and 109. ; 
S. arctica Linn. var bicristata Conrad (error for Sandberger?) 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 car- 
ine of the posterior cardinal margin; these are distinct and angular, with 
the intermediate space concave, and the crests of the carinz 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. 
