OF MOLLTJSCA. 87 



a. Tentacles simple. 



* Eyes on elongated pediceU, united to the short tentacles. Oper- 

 culum ovate, of few whorls. 



1. ASSIMINEA. 



Eyes on pedicels, united to the short tentacles. 



1. A. Gravi, t. 51. f. 8, t. 123. f. 6; Forbes fy Hanley, B. M. 

 t. H.H. f. 6. 



Central tooth of Assiminea Grayana (fig. 4S) wider below the 

 base, truncated in the middle, prominent on both sides, produced 



Kg. 48. — Teeth of Assiminea Grayana. 



into a horn ; cutting edge triangular, with from five to seven pointed 

 lobes ; first lateral tooth with seven teeth, the third tooth larger ; 

 second slender; scape narrow, claw-like, serrated on the outside; 

 the third rounded at the tip, ciliato-denticulate. — Lovbi. 



When the animal was first described in 1821, I observed that it 

 differed from all others of the Order in the eyes appearing to be 

 placed at the end of the tentacles, but I believed they were placed 

 on peduncles as long as the tentacles, the two being soldered toge- 

 ther; for if the pedicels of the eyes of this genus are minutely 

 examined, they seem to be formed of two parts united by a suture ; 

 and Mr. Berkeley observes, that it would appear as if there were in 

 Teality no tentacula, but only the tubercles common to many mol- 

 lusks at the base of the tentacles, a little more developed than usual. 



The genus Assiminea is an instance of shells very nearly allied in 

 external appearance having very different animals. The shell is not 

 to be distinguished from the smaller Littorince. 



"o" 



** Eyes nearly sessile, on outer side near the base of the tentacles. 

 •j- Operculum ovate, of few whorls. 



2. Littorina. 



Eyes sessile, on base of tentacles. Shell ovate, solid, imperfo- 

 rated ; spire short ; aperture ovate ; inner lip concave, outer simple. 

 Littoreal. 



1. L. littorea, t. 51. f. 4 ; Forbes §■ Hanley, B. M. t. G.G. f. 3 ; 



Adams, Gen. Moll. t. 33. f. 1. 



2. L. varia, t. 127 a. f. 2. 



