MYTILUS. 119 



a blunt point to a rounded edge, remarkably convex and gib- 

 bous, rather solid and glossy: sculpture, fine but irregular 

 lines of growth : colour beneath the epidermis yellow tinged 

 with purple : epidermis thick, yellowish-brown and of a darker 

 hue on the sides, exfoliated in all parts except towards the 

 anterior margin, and rising into numerous stiff beard-like 

 points of different lengths, those on the lower part of the 

 ventral side being the finest : margins thick, incurved on the 

 ventral side, rounded behind, both these margins being nearly 

 parallel, semicircular in front : byssal sinus narrow but dis- 

 tinct : beaks small, blunt, and inflected, lying horizontally on 

 the point of the shell, slightly diverging from each other, and 

 placed at a very short distance from the anterior margin : 

 hinge-line slightly curved, occupying less than two-fifths of 

 the dorsal margin : ligament thick and strong, very little ex- 

 posed : Idnge-plate solid, with a deep ligamental groove as in 

 the last species, and the rib is continued within the anterior 

 margin, so as to form a small vaulted chamber below the 

 hinge; inner edge of the dorsal margin finely crenulated 

 across : hinge thick and prominent, also finely crenulated or 

 toothed : inside nacreous and iridescent, purplish-yellow, and 

 stained with brown on the dorsal side and in front : scars in- 

 distinct. L. 0-65. B. 0-375. 



HABITAT : On all our coasts, from the extremity of 

 Shetland to the Land's End and Jersey, rather common 

 on rocky and hard ground from low- water mark to 86 

 fathoms. It appears to be a Coralline Crag fossil, as I 

 observed in Mr. Searles Wood's collection some speci- 

 mens mixed with the young of M. modiolus from that 

 deposit. Steenstrup found it in Iceland; and it has 

 been enumerated by all writers on the Scandinavian 

 mollusca as occurring from Vadso (near the North 

 Cape) southwards at depths ranging from 30 to 160 

 fathoms. A living specimen has been taken at Cannes 

 by M. Mace. It was first described by Philippi from 

 the upper tertiary beds of Calabria and Sicily. 



The animal is rather active when detached from its 

 byssus, using its extensile foot for creeping like its con- 

 geners, and moving with considerable agility. It often 



