350 TUPvRITELLID^. 



Syn. Ampulloidea, TJOrh. Ampullaroides, Gray. 

 Asolen, Agass. Asolena, Herm. 



Ex. A. Platee, Matou, pi. 37, fig. 7. Shell, A. Plata?, 

 fig. 7, a. 



The animal of this genus appears to be without the 

 respiratory siphon so conspicuous in the other genera of 

 the family. It is an inhabitant of the rivers of South 

 America. 



Fam. TURRITELLID^. 



Lingual membrane minute, very short, teeth in seven 

 series (3' 1*3), each series consisting of a subquadrate 

 median tooth, with an incurved denticulated apex, and of 

 three similar, ligulate uncini on each side, all with 

 hamate, serrulated summits. Rostrum short, broad ; ten- 

 tacles long and subulate, the eyes slightly prominent on 

 their external bases. Mantle with a fringed margin, 

 obscurely siphonated at the right side ; branchial plume 

 single, very long. Foot very short, truncate in front, 

 rounded behind, grooved beneath ; operculigerous lobe 

 simple. 



Operculum horny, circular, multispiral, edge of the 

 whorls fimbriated. 



Shell spiral, many-whorled ; aperture simple in front. 



This is strictly a marine group, the species ranging 

 from low-water mark to the depth of 100 fathoms; their 

 geographical distribution extends over most of the coun- 

 tries of the globe, one species being an inhabitant of 

 the British seas. In familiar language they are usually 

 termed " Screw-shells," on account of their peculiar 

 form; in organisation, they appear closely to resemble 

 Melania and Cerithium. As many as 170 species occur 



