GENUS \X\l. HALIOTIS. 135 



shell, and placed close to one end : most of the species are 

 very remarkable by having a spiral row of holes ; as the shell 

 increases in size new holes are formed ; the last fi\ e or six are 

 kept open, but the others are closed up by the animal : the 

 use of these holes is not well-known, but probably they are 

 for breathing through. 



The animal inhabitant is nearly allied to that of the suc- 

 ceeding genus : the head is cylindrical, which they extend a 

 very little beyond the edge of the shell, at the part furthest 

 from the spire ; they have two small slender horns, one on 

 each side the head, with the eyes at the extremity of two 

 short triangular columns placed a little behind the horns. 

 They have no operculum (see pi. 10. /. 3). 



Linnaeus describes 7 species, Gmehn has added 12, and 

 Dr. Turton none. Total, 19. 



Lamarck has divided this genus into two, as follow : 

 Stomatia. Shell oval or ear-shaped, with a prominent spire ; 

 the aperture large, entire, longer than wide ; the cUsk im- 

 perforate (see Haliotis iinperforata, pi. 9. /. 120). 

 Haliotis. Shell flattish and ear-shaped, with a depressed and 

 nearly lateral spire, and a spiral row of holes parallel 

 to the left edge ; the aperture very lai'ge, and long-er than 

 wide, entire (see Haliotis tuberculata, pi. 9. f. 121). 



