54 SYSTEMATIC ARRANGEMENT 



A. Ptenoglossa. Teeth in numerous longitudinal series (fig. 33). 



Fam. XXII. ACTEONID^E. 



Shell spiral, ovate, external. Teeth numerous, uniform, in a diver- 

 ging transverse series as in Bulla (fig. 33) . Tentacles broad, depressed, 

 united, and forming a shield on the head, notched in front. Eyes 

 on the inner side of the base of the expanded tentacles. Foot mode- 

 rate, dilated and partly reflexed on the sides. Mantle enclosed ; 

 " branchial plume single." Operculum horny, ovate, spiral ; few 

 whorls, with a thin flap on the inner edge. 



This family has many affinities to Bullidee ; indeed it may prove 

 to be part of that family.— Phil. Moll. Sicil. ii. 143. Alder and 

 others have placed Acteon in that family. 



1. Acteon. 



Shell thin, ovate, spirally striated ; spire short, acute ; mouth 

 lanceolate, narrow, rounded, and entire in front ; inner lip thin ; 

 pillar with a single oblique spiral fold. Operculum subspiral, horny. 

 I. A. Tornatilis, t. 128. f. 5 ; Forbes #■ Hartley, B. M. t. V.V. f. 7. 



The body of Acteon is spiral and compressed ; the edge of the 

 mantle free all round, slightly nicked in front, and with a slight fold 

 on the right side. The head is surmounted by two very broad, thin, 



Fig. 33.— Teeth of Acteon Tornatilis. 

 Fig. 32. — Acteon Tornatilis. 



expanded, membranaceous tentacula, forming a kind of hood, and 

 separated from each other by a longitudinal groove ; each of 'them 

 has a slit near the middle of its outer margin, the upper edge of the 

 left being expanded and rounded, while that of the right is much 

 larger, acute, and folded down. These tentacula bear some resem- 

 blance to the double fringed lips of Phasianella (see Cuv. Moll. 



1. 11. f. 2,3). Head distinct. Eyes ? Mouth sunk in. Foot 



short, folded across near the anterior part when the animal is con- 

 tracted, slightly nicked anteriorly and rounded behind. The animal 

 is unisexual. The penis exserted, large, situated near the base of the 

 right tentaculum. Branchiae pectinate. Operculum horny, exactly 

 the same shape with the mouth of the shell, attached to the upper 



