240 NEW FOSSIL SHELLS 



vato; natibus valde elevatis, acuminalis; in valvd utraque dentibus cardinalibus duobus, lateralibtis nullis; nymphis 

 curtis, crassis; lunula parvd, cordatd; cicatricibus maximis; cicatrice palleali valde sinuata. 



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- 

 phae short, thick; luuule 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 Area centenaria of Say. 



Judging from description, this shell must resemble the Petricola centenaria, Conrad, 

 but its nympha?, teeth and sinuated palleal impression, exclude it from that genus. It is 

 larger and more beautiful than any of its congeners. 



GENUS LUCINA. 

 L. PUNCTULATA, PL. 34. FIG. 18. 



L. testa rotunda, lenticulari, sub-cequilaterali, postice et antice truncato-rotundatd, convexd, tenui, diaphand, punc- 

 tulatd, substriatd; striis concentricis, irregularibus, ram; clivo umboniali rotundato; natibus prominentibus, acutis; 

 valvd sinistrd dentibus cardinalibus duobus^ laterali uno; margine interno integro. 



Shell rounded, lenticular, sub-equilateral, truncately rounded posteriorly and anteriorly, convex, diaphanous ? 

 punctulate, somewhat striate; striae 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 all its fossil congeners by its diaphanous 

 substance and punctulate surface. 



L. LENS, PL. 34. FIG. 19. 



L. testa orliiculari. cequilaterali, valde convexd, crassd, costatd; costis concentricis, parvis, crebrissimis, planulatis, 

 politis; margine dorsali fiexuoso; natibus prominentibus ; acutis, incurvis; lunula ellipticd, magnd, profunda; dentibus 

 in utraque valvd, cardinalibus duabus parvis : lateralibus duabus magnis; margine interno minute crenulato. 



Shell orbicular, equilateral, very convex, thick, costate; costse concentric, small, very numerous, flattened, polished ; 

 dorsal margin flexuose; beaks prominent, acute, incurved; lunule elliptical, large, deep; e,ach 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 striae, unless examined with a 

 microscope. There are occasional larger ones, where the shell appears to have ceased 



