62 PLEIOCENE FOSSILS. 



LUC IN A TEI SULCATA. — Con. 



Plate XVIII. Figs. 18 and 19. 



Lucina trisulcata, Con., Foss. Ter. For., p. 71, pi. 40, fig. 5. 



L. testa ovata, convexa, incequilaterali; concentrice striata, sulcata; lunula cordata, profunde 

 excavata. 



Description. Shell ovate, convex, inequilateral; concentrically striate and channelled; 

 lunule cordate, deeply excavated. 



This fossil resembles L. crenulata; but it is readily distinguished from that species by 

 its less orbicular outline, its prominent and more oblique beaks, and above all, by the short 

 but very deep lunule, which extends under the beaks. 



The concentric sulci which suggested the specific name to Mr. Conrad, are accidental, 

 quite variable in number and position, and in the larger number of individuals they are 

 absent altogether. 



The short and deep lunule will serve to characterise all the varieties of the species. 



Plate XVIII. Fig. 18, Natural size. 

 " 19, Magnified. 



Locality. Darlington District. 



The genus Lucina is found as low in the geological series as the devonian system, and 

 has its greatest development in the seas of the present period. 



