68 systematic arrangement 



6. Lanistes. 



Shell sinistral, subdiscoidal, perforated ; mouth ovate j lips simple. 

 Operculum horny, sinistral, or with nucleus on left margin. — Adams, 

 Gen. Moll. t. 37. f. 5 a, b (upside down). African. 



1. L. Bolteniana. 



2. L. ovum, Troschel, Naturg. 1845, t. 8. 



The animal of Lanistes is very like the Ampullarice. The front 

 of the head is bifid ; the concave processes of the forehead and the 

 tentacles are spirally twisted when contracted. There is a plate on 

 each side of the body, forming a canal on the neck. The penis is 

 contracted on the right side of the edge of the mantle. The air-bag 

 is distinct. Operculum horny, with a subcentral nucleus. Teeth 

 on lingual membrane 3 * 1 • 3 ; the central and inner lateral curved, 

 three-lobed ; the two outer lateral subulate, hooked. — Erichson,Arch. 

 1845, t. 8. f. 6. 



7. Meladomus. 



* 



Shell ovate, sinistral ; spire conical ; whorls convex ; periostraca 



olive ; mouth ovate ; lips simple. Animal ? Operculum 



horny, sinistral ; nucleus subcentral, rather near the left margin. — 

 Adams, Gen. Moll. t. 37. f. 6 a, b. 



I. M. olivaceus. 



II. Edriophthalma. Eyes sessile or nearly so, at the outer side 



of the base of the subulate tentacles. 



A. Cryptocochlea, Gray. Mantle of adult animal expanded and 

 often reflexed over the shell, which has a polished appearance. 



Fam. II. AMPHIPERASID.E. 



Shell involute. Mouth linear ; inner lip smooth. Lateral teeth 

 on tongue-membrane ; outer rugulose, broad, digitatelylobed (fig. 38). 

 Canal elongate, produced. Mantle lobes expanded, covering the sides 

 of the shell, bearded externally. 



The shell, when young, spirally striated; when adult, covered 



Fig. 38.— Teeth of Amphiperas ovum. 



) < ^V^ ) 



with B smooth enamel coat; the inner lip toothless, and the outer 

 toothed Or crenated; tin- anterior and posterior canal mostly elon- 

 gated, itraightish. 



