240 NEW FOSSIL SHELLS 
vato; notibus valde elevatis, acuminatis; in valvd utrdque dentibus cardinalibus duobus, lateralibus nullis; nymphis 
curtis, crassis; lunuld parvd, cordatd; cicatricibus maximis; cicatrice palleali valde sinuato. 
Shell transverse, ovately quadrate, inequilateral, gaping posteriorly, subtruncate anteriorly and posteriorly, very 
much inflated, very thick, sulcate ; sulci radiating, numerous, equal, wide; basal margin almost straight; dorsal margin 
slightly curved; beaks much elevated, acuminate; hinge in each valve with two cardinal and no lateral teeth; nym- 
phe short, thick; lunule small, cordate; cicatrices very large; palleal impression much sinuated. 
Diam. 1.25. Length 1.56, Breadth 2,30. inches. 
Remarks.—The radiating sulci are largest and deepest on the posterior extremity of the 
shell; they are interrupted by occasional lines of growth. The palleal impression becomes 
very broad as it approaches the anterior cicatrix. It is very rugose, and has a large, 
semi-elliptical sinus posteriorly. .In the right valve, one of the teeth is bifid, but, as in 
all my specimens the hinge of the left valve is fractured, I am unable to say whether this 
be the case in it or not. ‘The outline of the shell is very variable. I have one specimen 
which is nearly oblong, with a sinuated basal margin and almost central beaks, In this 
form its external appearance approaches closely that of the Arca centenaria of Say. 
Judging from description, this shell must resemble the Petricola centenaria, Conrad, 
but its nymphe, teeth and sinuated palleal impression, exclude it from that genus. It is 
larger and more beautiful than any of its congeners. 
GENUS LUCINA. 
L. punctunata, Pu. 34. Fie. 18. 
L.. testé rotundd, lenticulari, sub-equilaterali, postice et antice truncato-rotundatd, conveud, tenui, diaphand, punc- 
tulatd, substriatd; striis concentricis, irregularibus, raris; clivo umboniali rotundato; natibus prominentibus, acutis; 
valvé, sinistra dentibus cardinalibus duobus, laterali uno; margine interno integro. 
Shell rounded, lenticular, sub-equilateral, truncately rounded posteriorly and anteriorly, convex, diaphanous, 
punctulate, somewhat striate; strie concentric, few, irregular; umbonial slope rounded; beaks. prominent, acute; left 
valve with one lateral and two cardinal teeth; internal margin entire. 
Diam. .16. Length .32. Breadth .35 of an inch. 
Remarks.—The concentric lines of growth are, for the most part, very small, but there 
are two or three larger ones. ‘The punctulations extend over the whole surface. They 
are very small, and cannot be seen without the aid of a microscope, but they impart a 
rough feeling to the shell when handled. 
This shell may be readily distinguished from al] its fossil congeners by its diaphanous 
substance and punctulate surface. 
L. tens, Pr. 34. Fie. 19. 
L. testa orbiculari, equilaterali, valde convexd, crassd, costatd; costis concentricis, parvis, crebrissimis, planulatis, 
politis; margine dorsali flexuoso; natibus prominentibus, acutis, incurvis; lunuld ellipticd, magna, profundd; dentibus 
in utraque valud, cardinalibus duabus parvis, lateralibus duabus magnis; margine interno minute crenulato. 
Shell orbicular, equilateral, very convex, thick, costate ; costs: concentric, small, very numerous, flattened, polished ; 
dorsal margin flexuose; beaks prominent, acute, incurved; lunule elliptical, large, deep; each valve with two small 
cardinal, and two large lateral teeth ; internal margin minutely crenulate. 
Diam .28. Length .35. Breadth .38 of an inch. 
Remarks.—The ribs are very small, and appear like strie, unless examined with a 
microscope. There are occasional larger ones, where the shell appears to have ceased 
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