LITHOPHAGID^E. MOLLUSCA. SAXICAVA. 61 



broadly rounded, especially the posterior tip ; basal margin scarce- 

 ly curved and nearly parallel with the superior margin ; surface 

 marked with the lines of growth, eroded at the beaks, and covered 

 with a purplish or dirty- brown rather thick epidermis. Within 

 white and glossy ; two muscular impressions and the palleal line 

 directly connecting them, without any sinus, quite perceptible. 

 Hinge consists, in the right valve, of a narrow, erect, central tooth, 

 and an imperfect one each side, slightly detached from the edge 

 of the valve ; in the left valve, of a well-defined tooth on each 

 side, barely separated from the edge of the valve, leaving a tri- 

 angular vacancy between them to receive the central tooth of the 

 opposite valve. Length | inch, height | inch, breadth T ^ inch. 



Several specimens of this minute shell were found by Mr. C. 

 F. Shiverick in the harbour of New Bedford. I have also found 

 it about the roots of sea-weed, which seems to be its proper 

 station. 



The arrangement of the teeth does not seem to be well expressed 

 in the generic description ; but as they accord precisely with those of 

 a specimen of K. sub-orbiculdris sent me by Dr. Loven, I do not 

 hesitate to place our shell under the genus. I cannot find that it dif- 

 fers essentially from the foreign K. rubra, except that its color does 

 not appear to be of so bright a red as Montagu's figure. 



FAMILY LITHOPHAGWM, LAM. 



Shell burrowing, but without a tube or accessory valves, more or less gap- 

 ing ; ligament external. 



GENUS SAXICAVA, LAM. 



Shell transverse, inequilateral, gaping posteriorly and above ; 

 hinge nearly toothless. 



SAXICAVA DISTORTA. 



Shell oblong, inequivalve, rounded before, and generally trun- 

 cated behind, and with a prominent ridge running from the beaks 

 to the lower posterior angle ; surface rough and irregular. 



FIGURE 40. 

 State Coll., No. 243. Soc. Cab., No. 1751. 



