CONCHOLOGY. 75 



a mantle closed above, open below, and especiall}'^ to the rear, 

 where it forms sometimes a sort of tube furnished with tentacular 

 cirri : a flabelliform abdominal appendage, and a very consider- 

 able byssus ; mouth provided with double lips, beside two pairs of 

 labial appendages ; a single large retractile muscle apparent. 



Shell. Subcornate, fibrous, brittle, regular, equivalvc, longi- 

 tudinal, triangular, pointed anteriorly, in which direction is the 

 summit, which is straight, wide, and frequently truncated poste- 

 riorly ; hinge dorsal, longitudinal, linear, toothless ; ligament occu- 

 pying nearly all the dorsal edge of the shell ; a single and very 

 wide muscular impression posteriorly ; a trace of the anterior in 

 the summit. Inhabits the Mediterranean Sea. Fifteen species. 



Pinna rudis. Pinna flabellum. 



P. seminuda. P. angustina. 



P. nobilis. P. squamosa. 



P. marginata. P. muricata. 



P. pectinata. P. saccata. 



P. ingens. P. dolabrata. 



P. varicosa. P. vexillum. 



P. nigrina. 



FAMILY XVII. 



Malleacea. Five genera. 



1. Genus Crenatula. PI. VIII. 



Anivial. Unknown. 



Shell. Irregular, much flattened, subrhomboidal, subequivalve, 

 gaping posteriorly ; summit anterior ; hinge longitudinal, dorsal, 

 toothless ; ligament submultiple, or inflated from place to place, 

 and inserted in a series of round cavities corresponding with the 

 dorsal edge ; muscular impression unique and subcentral. In- 

 habits the Red Sea. Seven species. 



Crenatula modiolaris. Crenatula bicostalis. 



C. avicularis. C. viridis. 



C. nigrina. C. mytiloides. 



C. phasianoptera. 



