114 MYTILUS. MUSSEL. 



those large detaehed masses which are scattered under 

 the cliff at Torquay, near the entrance to the strand from 

 the Tor-abbey fields. The Mytilus lithophagns, indepen- 

 dently of the transverse striae which cross the concentric 

 ones on the cartilage side, is very convex and rounded on 

 the back, giving the shell a somewhat cylindrical appear- 

 ance when the valves are closed ; the beaks are also ter- 

 minal and somewhat pointed, like those of the M. Modio- 

 lus, with the opposite extremity rounded. Mr. Dillwyn 

 has referred Lister's figure (which is an excellent one, and 

 marked as English,) to the Solen minutus, which is trun- 

 cate at the hinge end. Those which we have collected 

 from among the roots of Fuci and Sertularias, are much 

 more irregular in their figure, but all sufficiently retaining 

 their specific marks, v. v. 



13. Mytilus plicatus. Plaited Mussel 

 Chemn. Conch, viii. pi. 82. f. 733. a, b. 



Shell oblong, very thin, transparent, dirty white, uneven 

 on the surface, slightly plaited and irregularly wrinkled 

 transversely, rounded on the side next the hinge, angular 

 and dilated on the other, causing it to be a little larger, 

 where it gapes ; inside glossy, rather perlaceous : hinge 

 near the rounded and smaller end : beaks small, a little in- 

 curved : length not half an inch; breadth double its length. 



Jsle of Sky, and Dublin bay : rare. v. m. 



14. Mytilus decussatus. Decussated Mussel. 

 Chemn. Conch, viii. pi. 85. f. 761. 



Shell longitudinally oval, thin, transparent, very convex, 

 covered with a pale olive skin, under which it is pearly 

 white, finely striate longitudinally, and crossed by more 

 minute transverse lines ; inside smooth, perlaceous ; the 

 sides equal ; beaks close to the smaller end, with a slight 

 indenture, and the contiguous margin is faintly denticu- 

 late ; and near the front margin is a singular reflected trans- 

 verse ridge : length the eighth of an inch ; breadth not so 

 much. 



Only one, valve of this shell was found by Captain Las- 

 key, on the Scotch coast : its convexity gave it the appear- 

 nnce of a Patella j but the hinge is that of a bivalve desti- 

 tute of teeth, w 



15. Mytilus 



