FROM THE TERTIARY OF VIRGINIA. 237 
As but one valve of this shell, and that the left one, is before me, [ cannot determine 
the shape of the tooth. The pit to receive it is small and almost horizontal. 
This is, I believe, the only extinct species of Mya as yet found in our Tertiary. 
GENUS THRACIA, (Leacu.) 
T. TRANSVERSA, Pu. 34. Fie. 11. 
T. test sub-ellipticd, valde inequilaterali, postice acuminato-rotundatd, antice truncatd, sub-compressd, tenui, 
medio levi, postice et antice concentrice striatd; clivo wmboniali rotundato; margine basali curvato; margine dorsali 
medio angulato, postice convexo, anticé concavo; natibus sub-acutis; callo nymphali parvo, obliquo. 
Shell sub-elliptical, very inequilateral, acuminately rounded posteriorly, truncate anteriorly, sub-compressed, thin, 
smooth centrally, striate posteriorly and anteriorly; umbonial slope rounded; basal margin curved; dorsal margin 
angular in the middle, posteriorly convex, anteriorly concave; beaks somewhat acute; nymphal callosity small, 
oblique. 
Diam. .10. Length .18, Breadth .28 of an inch. 
Remarks.—F rom the shape of the anterior margin, I conclude that the shell must have 
gaped considerably there, but as I have no pair of valves, I cannot be certain. The sinus 
of the palleal impression is deep, and near the anterior cicatrix. In this character, it 
differs from the rest of the genus. 
This is, I believe, the first Thracia found in our Tertiary deposites. Deshayes, in his 
tables, gives four as the number of European Tertiary species. The present one is the 
smallest of the genus. 
xENUS ANATINA. 
A. TELLINOIDES, Pu. 34. Fic. 12. 
A. testé ovato-triangulari, transversd, postice angulatd, antice rotundatd, compress, postice undulatd, tenui, con- 
centrice striatd; striis crebris minutis; margine basali sub.flenuoso; natibus compressis, prominentibus; dentibus 
lateralibus magnis; cochled obliqud, ovato-acuminatd, minime profundd; cicatricibus magnis. 
Shell ovate-triangular, transverse, angular posteriorly, rounded anteriorly, compressed, posteriorly undulate, thin, 
concentrically striate; striae numerous, minute; basal margin slightly flexuose ; beaks compressed, prominent; lateral 
teeth large; fosset oblique, ovate-acuminate, shallow; cicatrices large. 
Diam. .25. Length .45. Breadth of an inch. 
Remarks.—Of the lateral teeth, the posterior one is much the longer. The fosset is 
small, quite oblique, acute above and rounded below. ‘The broad undulation on the pos- 
terior part of the shell gives it very much the appearance of a 'Tellina, when viewed 
externally. The lines of growth are small, very numerous and irregular. 
This species is quite thin and fragile. Out of some half a dozen specimens, I have but 
one perfect valve, and that is a very young one. Iam therefore unable to give all the 
dimensions. 
Judging from description, this shell is not unlike the A. antiqua, Conrad, but the dif- 
ference in size and sculpture, and the posterior undulation distinguish them at once. 
VOL. Ix.—63 
