112 MYTILID.E. 



curved, placed a little below the point of the shell and at a 

 short distance from the anterior margin: hinge-line gently 

 curved, occupying nearly the upper half of the dorsal margin : 

 ligament extremely strong, partly exposed : hinge-plate solid : 

 hinge toothless, reflected: inside nacreous and often studded 

 with incipient pearls : muscular and jjallial scars very distinct. 

 L. 5. B. 2-5. 



Var. 1. ovata. Shell smaller, narrower at the smaller end 

 and broader at the other. L. 3. B. 2. 



Var. 2. umbilieata. Shell narrower ; anterior margin in- 

 flected and forming a deep sinuosity. M. umbilicatus, Penn. 

 Brit. Zool. iv. p. 112, pi. 65. f. 76. 



Habitat : Coasts of England, Wales, Ireland, and 

 Scotland, from low- water mark to 80 fathoms, and at a 

 distance of more than forty miles from land, in muddy 

 gravel. It is not common in the first two localities, 

 but abundant and gregarious in the north and west of 

 Scotland and Shetland, at depths varying from 2 to 

 20 fathoms. Var. 1. Lismore (Bedford) ; Portmarnock 

 and county Antrim (J. Gr. J.). Var. 2. Cork Harbour 

 (Humphreys). The species occurs in all our upper ter- 

 tiaries, and especially in the glacial beds. It ranges 

 from Behring's Straits (Wosness), New England (Stimp- 

 son), and Iceland (Steenstrup) to the Danish coasts of 

 the Baltic ; but I am not aware that it has been noticed 

 further south. In Calabria, however, it is fossil, and was 

 described by Philippi under the name of Mocliola grandis. 

 This is another proof of arctic conditions having for- 

 merly pervaded the South of Europe. 



Pennant must have considered this to be a fish, when 

 he says it " often seizes the bait of the ground-lines." 

 It is now and then caught by the beard and hooked up 

 in this way. In some parts of Shetland and the north 

 of Ireland it is eaten by the poorer class ; and every- 

 where it is reckoned an excellent bait for fish. The epi- 



