OF MOLLUSCA. 161 



the keel ; aperture suborbicular. Operculum circular, horny, thin, 

 subspiral. 



1. S. laevigata, If Orb. 



Fam. VIII. HALIOTID.E. 



Operculum none ; frontal lobes none ? Mantle with a slit, and 

 shell with a series of holes on pillar side. Gills two, separate on 

 pillar side. Shell ear-shaped, with a series of holes over the mantle- 

 slit, pearly within ; adductor muscle single, central. 



a. Foot moderate, not produced, and grooved behind. Shell rugose. 



1. Haliotis. 



Shell ear-shaped, oblong, with a spiral ridge on the left side, with 

 holes in front which are gradually filled up behind as new ones are 

 formed in front. 



1 . H. tuberculata, t. 109. f. 2, 2 a, 6, 1. 1 10. f. 5, 7 ; Forbes fy Han- 

 ley, B. M. t. C.C. f. 3. 



Central tooth of Haliotis tuberculata small, depressed at the base, 

 rounded and produced, above covered with a convex plate which is 

 wider and unarmed ; inner one on each side single, transverse, beam- 

 Fig. 87. — Teeth of Haliotis tuberculata. 



like, deeply notched on the inside, rounded on the outside, furnished 

 behind beyond the middle with a spire ; lateral series of teeth about 

 seventy ; first four by far the largest, wide and misshapen ; hook of 

 the first rounded, of the second and third lanceolate, at the flexure 

 notched or denticulated, of the fourth short and triangular ; the 

 others somewhat equal in size, with an oval hook, denticulated behind 

 at the bend (fig. 87). 



Haliotis, in common with Fissurella, has a double symmetrical 

 branchial plume, two auricles, and a ventricle embracing the rectum, 

 which terminates between the roots of the branchiae. No operculum. 



M 



