101 
Saxicava. Lamarck. 
(Jen. Char. A transverse, inequilateral, hi 
valved shell ; anterior extremity gaping ; 
hinge with an external ligament, and only 
rudiments of teeth. 
The shells of this Genus inhabit holes in stone, not of 
their own making, to the size of which they are 
obliged to conform, consequently they are often much 
distorted and rugged : the muscular impressions are 
strong, and the attachment of the mantle is marked by a 
row of irregular cicatrices, of which the central one is 
larger than the others ; the tubes of the animal are long 
and projecting. 
SAXICAVA rugosa. 
TAB. CCCCLXV1. 
Spec. Char. Ovate, gibbose, rugged, both ex- 
tremities blunt, upon the disk of the anterior 
side are sometimes two rows of irregular 
short spines. 
Syn. My til us rugosus, Linn . Pennant , 
Biapholius rugosus, Leach , MSS. Saxicava 
rugosa, Lamarck Hist. Nat. V. 501. 
Var. spinosa , Solen minutus, Linn . fyc. Lam . 
Hist . Nat. V. 453. Biapholius spinosus, 
Leach MSS. 
However rugged the individuals of this common species 
may be, there is generally an angular ridge that marks 
the anterior side* ; between this and the upper edge are 
sometimes two rows of concave, irregular spines ; at 
*That is, the side from which the tubes are protruded ; we are aw are 
that some Authors consider this posterior, but we think it best not to 
change the term in this p*rt of the work. 
