1872.] HICKS TREMADOC ROCKS. 49 



very narrow. Sulcus well defined, but not as deep as in O. primceva, 

 pallial margin indented, anterior and posterior edge rounded. Beak 

 prominent, and general surface well raised. Concentric lines of 

 growth shown, but not very strong. 



I have named this species after Mr. J. Logan Lobley, F.G.S., 

 whose tabulations of this and other classes of the Mollusca form 

 important contributions to palaeontology. 



Loc. Ramsey Island and St. David's. 



Davidia, gen. nov. 



Ovate, umbo subcentral, nearer anterior extremity, both extremities 

 nearly equal in width. Surface of shell raised, and almost ridged 

 between umbo and each end near the cardinal margin. Hinge-line 

 more or less straight, about a third of the length of the shell, and 

 extending equally on each side of the umbo. Lines of growth 

 strongly marked. 



The subcentral umbo, equal extremities, and almost triangular 

 shape of the shell are important characters, and sufficient to stamp 

 it a new genus. 



Davidia ornata, spec. nov. PI. Y. fig. 12. 



Ovate, f -| of an inch long and rather less than J- wide ; beak raised, 

 with a strong ridge extending from it to each extremity. Surface 

 of shell marked with very strong lines of growth, posterior surface 

 in addition covered by transverse striae, converging obliquely from 

 margin to umbo. Hinge-line straight. 



Loc. Eamsey Island and St. David's. 



Davidia plana, spec. nov. PI. V. fig. 13. 



Ovate, nearly an inch long, and rather less than half an inch 

 wide, both extremities abruptly rounded. Beak pointed and slightly 

 incurved. Shell evenly but strongly raised in a line from the umbo 

 to the extremities. Hinge-line slightly convex. Lines of growth 

 marked but not very strong. This species differs from D. ornata in 

 having a less straight hinge-line, less strong lines of growth, and in 

 the want of the transverse striae on the posterior surface. 



Loc. Bamsey Island and St. David's. 



Modiolopsis ramseyensis, spec. nov. PI. V. fig. 14. 



Ovate in form, over an inch long by rather less than half an inch 

 wide. Strongly raised along hinge-margin, and inflated. Anterior 

 extremity short and rounded obtusely ; posterior long and pointed. 

 Beak incurved ; pallial margin strongly convex. Hinge-line long. 

 Surface covered by concentric lines of growth. 



Loc. Eamsey Island and Tremanhire. 



Modiolopsis Homfrati, spec. nov. PL V. figs. 16 & 17. 



Ovate, greatly elongated, over an inch in length by about a fourth 

 of an inch in width. Anterior extremity short and rounded ; posterior 



VOL. XXIX. — PART I. E 



