PATELLA. 423 



slightly raised simple striae, with which the entire surface 

 is densely covered. 



Aged shells have usually a more rounded contour, and 

 greater elevation ; their obtuse vertices are rather more 

 central than in the young. These last display a richer 

 style of colouring than the more mature individuals, being 

 not unfrequently of an orange red, with the inside beauti- 

 fully iridescent and adorned with rays of a bright red ; 

 the spatula at that stage of growth is not yet developed. 

 In some the ribs are roughened by nodulous projections, 

 but these nodules are irregular, generally few in number, 

 and not fang- shaped. Sometimes they are large and 

 blunt (in which case the ribs are broad and strong) ; some- 

 times, too, there are crowded vaulted scales upon the cos- 

 tellee, owing to the more than ordinary projection of the 

 closely set concentric wrinkles, which, although delicate, 

 are always more or less apparent upon the surface. These 

 examples form the nearest approach to athletica, especially 

 when the ribs are nearly white ; and were it not for the 

 different colour of the substance of the shell, might, at a 

 stage when the whole of the distinctive features are not 

 developed, be readily mistaken for that species. 



Our larger examples measure twenty-eight lines in 

 length, and twenty-three in breadth. 



The animal is of a general bluish or dusky hue; its 

 head is dusky with long, strong, conical tentacula, which 

 are tinged towards their extremity with a bluish or dusky 

 tint, and bear a small black eye on the outside of each 

 of their swollen bases : when the creature is at rest it 

 bears its tentacles contracted and oppressed with their 

 tips curled towards each other. The lips of the mouth 

 are puckered, thickened above, and at the sides narrow, 

 and as if emarginate below. The jaws are tinged with 



