105 



Mytilus abbreviatus Mytilus inrurvatus 



retusus lineatus 



Hesperianus lacunatus 



[And two fossil species.] 



PINNA. 



pinna rldis. — Linn. 



Mawe's Linnaeus, plate 17- 



This genus has not undergone any division or altera- 

 tion by Lamarck. The shells of it are marine, some- 

 times attaining upwards of two feet in length, fragile, 

 of a longitudinal form, narrowed to a point at the base, 

 in the figure of an acute angled triangle, the upper end 

 open and truncated or rounded ; valves convex, arm- 

 ed with tubular spines, vaulted scales, imbrications, or 

 striae; some with an angle longitudinally placed at 

 the sides; in other species, the valves are rather round- 

 ed at the upper end, and in the shape of an expanded 

 fan: the ligament of the hinge is marginal, exter- 

 nal, and so extremely narrow and confined, that the 

 valves are capable only of a very limited expan> 

 sion, and appear as it were soldered together. The 



