244 NEW FOSSIL SHELLS. 
N. carinata. Pu. 34. Fie. 28. 
N. testa transversd, ovato-acuminatd, subinequilaterali, antic rostrata, postice rotundatd, inflata, crassiusculd, con- 
centricé sulcatd ; sulcis parvis, crebris, regularibus, rotundatis; clivo umboniali elevato, carinato; margine basali cur- 
vato; margine dorsali medio angulato, postice convexo, antice concavo; natibus minimé elevatis, recurvis; dentibus 
angulatis, carinatis; anticis quatuordecim, posticis quindecim; cochled triangulari, profundd; margine interno 
integro. 
Shell transverse, ovate-acuminate, sub-inequilateral, anteriorly rostrate, posteriorly rounded, inflated, rather thick, 
concentrically sulcate; sulci small, numerous, regular, rounded; umbonial slope elevated, carinate; basal margin 
curved; dorsal margin angular in the middle, posteriorly convex, anteriorly concave; beaks very slightly elevated, 
recurved ; teeth angular, carinate, fourteen anterior, fifteen posterior ; fosset triangular, deep; internal margin crenu- 
late. 
Diam. .15. Length .18, Breadth .11 of an inch. 
Remarks.—The teeth are large and angular, with a carina on the outside edge of the 
angle. The two series are nearly equal in number. 
This shell is very similar to the N. concentrica, Say: the points of difference are, 
however, the greater proportionate length of our species, its carinate umbonial slope, 
and peculiar teeth. It is also more equilateral, and has the series of teeth more nearly 
equal. In these two last characters, it also approaches the N. media, Lea. 
N. acutipens, Pu. 34. Fic. 29. 
N. testé tenui, levi, polita; dentibus magnis, longissimis, arcuatis, acutis, perpendicularibus ; cochled minime pro- 
funda. 
Shell thin, smooth, polished; teeth large, very long, arcuate, acute, perpendicular; fosset shallow. 
Diam, —— Length Breadth 
Remarks.—I have but a fragment of the hinge of this shell, but the teeth are so re- 
markable that they appear to distinguish it from all our other species. They are very 
long, thin, pointed, and placed perpendicularly to the hinge margin, so as to project 
beyond the shell and be seen nearly as well externally as internally. 
of an inch. 
FAMILY MYTILIDA. 
GENUS MODIOLA. 
M. spintcera, Pu. 35. Fia. 30. 
M. testd quadrato-ellipticd, transversd, inequilaterali, postice truncatd, antice rotundatd, sub-inflatd, tenui, dia- 
phand, striald; striis parvis, concentricis, irregularibus; clivo umboniali angulato; margine basali recto; margine 
dorsali recto, spinoso; natibus prominentibus, rotundatis. 
Shell quadrately-elliptical, transverse, inequilateral, posteriorly truncate, anteriorly rounded, somewhat inflated, 
thin, diaphanous, striate; strim small, concentric, irregular; umbonial slope angulated ; basal margin straight; dorsal 
margin straight, spinous; beaks prominent, rounded. ; 
Diam .08 of an inch. Length .10. Breadth .14, 
Remarks.—The spines on the dorsal margin are rather short and few in number; they 
project perpendicularly from the line of the margin. The substance of the shell is ex- 
tremely thin. The beaks are long and somewhat incurved. 
