44 PALEONTOLOGY OF CALIFORNIA. 



LIMA RECTICOSTATA, Meek. 



PL 7, Fig. 5. 



THE only specimen of this fossil in the collection is a cast of a right valve with 

 the margin of the anterior side broken away: I was at first inclined to think it 

 might be the right valve of the last-described species ; but, on a more careful com 

 parison, it was found to differ so materially in form, the straightness of its costae, 

 &c., as to lead to the conclusion that it can scarcely be the right valve of that 

 shell, unless it belongs to an undescribed genus. Hence it has been thought better 

 to view it, provisionally, as a distinct species. 



It is much compressed, and presents a rhombic-oblong outline, 

 as seen with a portion of the anterior margin broken away ; the 

 length being considerably less than the diameter from the hinge 

 to the ventral margin. Its hinge-line is rather short, and ranges 

 at right angles to the longer diameter of the shell. No remains 

 of ears are visible, the posterior margin rounding apparently into 

 the hinge-margin above. The beak is located anteriorly, and 

 surface ornamented by eleven simple, straight costse, which radiate 

 backwards and downwards from the beak. The costse are rather 

 prominent, a little narrower than the depressions between, and 

 present (in the cast) a roughened, irregularly subnodulosc ap 

 pearance, produced by concentric markings, which are also visible 

 in the depressions between the ribs. 



LIMA ? CUNEATA, Meek. 



PI. 7, Fig. 6, and 6 a. 



SHELL (right valve) obliquely subtrigonal, or suborbicular : 

 moderately convex, particularly in the central and posterior 

 regions, but cuneate anteriorly; posterior side obliquely trun 

 cated? anterior margin concave in outline above, where it is 

 truncated obliquely forward and downward, to near the pro 

 minent middle, from which point it rounds into the rounded 

 base; posterior umbonal slope prominent, and very distinct from 

 the flattened ear above, in consequence of the abrupt inflection 



