16 STREPTAXID^. 



Streptaxis, Gray, 1831. 



Syn. — Artemon, Beck, 1831. 



Distr. — 15 sp. Mostly South American; Africa; East Indies. 



Shell oval, heliciform but often oblique, profoundl}^ umbili- 

 cated ; whorls rapidly enlarging, deviating from the original 

 axis more or less ; aperture lunar, with or without teeth ; lip 

 slightly thickened and reflected. 



The principal character of the group is found in the singular 

 oblique spiral of the whorls causing a torsion of the axis of 

 revolution. 



ARTEMON, Pfeiffer, 1855. (Epistylia, Pfr., 1811.) Aperture 

 without teeth ; shell subregular. American. S. candidus, Spix. 



SCOLODONTA, Doring. Shell similar to that of Hyalina. Front 

 part of the animal elongated ; teeth of the radula dagger-shaped, 

 the median very short, rhombic. S. Seniheri, Doring. Argen- 

 tine Republic. 



AMMONOCERAs, Pfeiffer, 1855. Shell depressed orbicular, 

 shining, pellucid, thin, radiately striate ; umbilicus wide, per- 

 spective ; spire rather flattened ; last whorl not descending at 

 the aperture, the periphery rounded ; aperture large, rounded 

 lunate ; lip simple, acute, its extremities approaching. S. omo- 

 lomorpha, Orb. 



DisoARTEMON, Pfeiffer, 1855. Shell eonoidal or discoidal ; 

 parietal wall and outer lip armed with teeth. S. discus, Pfr. 



EUSTREPTAXis, Pfcifler, 1811. Typical group. S. contusus, 

 Per. (xcii,55j. *S'. comboides, d'Orb. (xcii, 56). S. deformis^Fev. 

 (xcii, 5T). 



ODONTARTEMON, Pfeiffer, 1855. Shell ovate; parietal wall and 

 outer lip armed with teeth. S. bulbulus, Morelet. 



Omphaloptyx, Bottger, 18Y5. 



Distr. — Hesse. 0. supracostata, Bottger. Fossil. 



Shell heliciform, subperfo rated, conical and costulated above, 

 smooth below ; last whorl very large, a little contracted at the 

 aperture; aperture small, a little oblique, semilunar; outer lip 

 simple, sharp ; columella thickened at the base, reflected over 

 the umbilical perforation ; parietal wall with a horizontal plica- 

 tion. Is supposed to be related to Streptaxis. 



Ennea, H. and A. Adams, 1855. 



Distr. — 58 sp. Africa, Mauritius, Madagascar, India, etc. 

 E. Liberiana, Lea (xcii, 58). Liberia. 



Shell subc3dindricar, slightly rimate, apex obtuse, smooth, 

 shining, hyaline ; whorls flattened, the last narrow, sulcate 

 externall}^ in the middle, lamellate within, with a strong plait 

 parallel to the columella; aperture subcircular; parietal lamella 

 extending inwards and situated close to the right margin ; 



