GASTEROPODA. 



169 



Atlas. Lesueur. — Shell none. Animal, having the 

 body divided into two parts, which are connected by means 

 of a kind of stalk ; the hinder portion is oval, the front 

 enlarged and thickened outwardly, and the edges ciliated ; 

 a small distinct foot beneath, and a pair of very small ear- 

 shaped tentacula above ; the anal opening is in the middle 

 of the right side of the hinder portion ; the breathing 

 organs are not yet known. 



A. Peronii is the only species. 



Oxynoe. Rqftnesque. — Shell Bulla-shaped, with simple 

 whorls and spire, situated at the fore part of the back of 

 the animal, which has the gills obliquely streaked at the 

 edges ; the mantle extended into two side wings ; and two 

 inflexible tentacula. 



One species found in the Mediterranean. 



Action. Montf. (Solidula Fischer ; Tornatella ; 

 Dactylus Schum. ; Speo Bisso.) — Shell small, 

 oval, and usually transversely striped ; spire 

 small, and pointed ; columella having one or 

 two thick plaits ; outer lip thin ; operculum 

 small and horny. Animal, not investing the 

 shell ; the head is a quadrate disk, bilobed in 

 front, and bearing two broad obtuse, semicircular 

 lobate tentacula, capable of reflexion on the shell 

 posteally, at the upper or inner base of which are im- 

 pressed two small eyes ; no central teeth on tongue, many 

 uncinated laterals ; mantle closed in front, its lateral lobes 

 slightly reflected on the shell ; branchial plume single ; 

 foot oblong, truncate in front, obtuse behind.* — few 

 species ; also fossil. 



The shells of this genus are found on the shores of the 



* Forbes's British Moll. 



