PHOLAS. Ill 



monstrosity from the same material as well as from 

 sandstone. The furrow or groove in the latter case is 

 quite accidental, and does not even extend to the beaks. 

 It was probably caused by an injury or obstruction of 

 the mantle in front. I have already noticed similar 

 cases in other conchiferous mollusks; and the uni- 

 valves are also subject to this kind of partial deformity. 

 P. parva has been observed by De Gerville and many 

 other conchologists in the north of France, by M^Andrew 

 at Malaga (of small size), and by Weinkauff at Algiers. 



On a fine living specimen, which I took out of its 

 burrow in sandstone at Exmouth, was a Tru7icatulina, 

 full of sarcode. It still adheres to the crest of 

 one of the ridges on the most exposed part of the 

 anterior side of the Pholas. Is it possible that this 

 part of the shell could have been employed in grinding 

 the stone, and that the delicate Foraminifer remained 

 uncrushed ? In the instance just mentioned the pos- 

 terior side of the Pholas was more worn than the 

 other. Sometimes the entire sculpture of the shell is 

 quite perfect, and appears not to have suffered the 

 slightest attrition. The oval shape, smaller size, close 

 and delicate sculptm'c, wide gape in front, large tubercle 

 on the hinge-plate, and more central position of the 

 hinge will readily serve to distinguish P. parva from P. 

 Candida. My largest specimen is 2\ inches in breadth. 



Da Costa, Boys, and Donovan mistook the young of 

 P. crispata for the present species ; and it is not un- 

 likely that they were misled by Pennant, judging from 

 his ambiguous description and figure. The last-named 

 author confounded his species with Martesia striata. 

 Our shell may have been known to Lister, who says, 

 with reference to P. crispata, that sometimes it has a 

 third small shell at the hinge. Solander called it P. 



