101 



Saxicava. Lamarcli. 

 Gen. Char. A transverse, inequilateral, bi- 

 valved shell ; anterior extremity gaping ; 

 hinge with an external ligament, and only 

 rudiments of teeth. 



X HE 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. CCCCLXVl. 



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. Mytilus rugosus, Linn. Pennanty ^c. 

 Biapholius rugosus, Leacliy MSS. Saxicava 

 rugosa, Lamarck Hist. Nat. V. 501. 



Var. spinosa, Sol en minutus, Linn. Sfc. 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 aware 

 that some Authors consider this posterior, but we think it best not to 

 change the term in this part of the work. 



