MYTILUS. 173 



more beautiful thin and semi-transparent shell, has a 

 brownish-yellow epidermis, beneath which the surface is 

 either uniform white, which is very rarely the case, or 

 adorned with a very variable number of narrow and occa- 

 sionally even linear blue rays on a pale ground ; the in- 

 terior is of an uniform somewhat nacreous white, but never 

 opaline. 



The entire shell is devoid of sculpture; the epidermis is 

 more or less glossy, rarely if ever either quite dull, although 

 generally but little shining or highly polished. The com- 

 pressed basal area is usually narrow, and generally termi- 

 nates rather abruptly behind. The beaks are pointed, 

 quite terminal, and diverge a little from each other. The 

 hinge-margin is not crcnulated (a ready mark of distinc- 

 tion from the minimus of Poli and Philippi, which looks 

 like a dwarf specimen of it) ; there are no real teeth, but 

 about four narrow denticles, usually concealed by the over- 

 lapping epidermis. 



Ordinary sized English specimens do not much exceed 

 two inches and a half in length, and about half that 

 breadth. Mr. Barlee, however, has an example from Loch 

 Fyne which measures eight inches and a half! 



The Mytilus striatus of the English writers (Mont. Test. 

 Brit. p. 173. — Trans. Linn. Soc. vol. viii. p. 112) solely 

 constructed from a figure (75) in Walker's " Testacea 

 Minuta Rariora," and surmised by Montagu to be possibly, 

 if indeed a shell at all (which we much doubt), the fry of 

 the large Modiola, is cited by Turton for the young of this 

 species. 



Animal shaped as the shell, thick, the margins of the 

 mantle freely open in front and in the branchial region, 

 united to form a tube only in the anal region. They are 

 quite simple anteriorly near the beaks, serrated towards 



