92 ODONTOSTOMUS. 



little flattened near the upper end of the outer lip. Aperture sub- 

 vertical, ovate, less than half the total length of the shell ; peristome 

 white, narrowly expanded, the columellar margin dilated, parietal 

 callus thin ; columella oblique but foldless. 



Length 22, diam. 9, length of aperture 9 mill. (Doering's type). 



Length 22.5, diam. 8, length of aperture 9.6 mill. (Golfo Nuevo). 



Length 19, diam. 7, length of aperture 8 mill. (S. Ventana). 



Length 16.8, diam. 7, length of aperture 7.5 mill. (S. Ventana). 



Argentina: Sierra de Currumalan, living with 0. rocse on 

 quartzite rocks ; Sierra Ventana, around Fuerte Argentine (Doer- 

 ing); Golfo Nuevo or Bahia Nuevo (von Ihering). 



Eudioptus avellanedae DOER., Informe Oficial de la Comision 

 Cientifica Exped. al Rio Negro, Zool., p. 64, pi. 1, f. 2, 3 (1881). 

 Anctus (?) stearnsianus PILSBRY, Nautilus x, p. 41 (1896). 



A slender species, not very unlike the Argentine group of Buli- 

 mulus (Vol. x, p. 191), but more allied to Odontostomus or Anctus in 

 the building forward of the aperture-margins. I have little doubt 

 that it holds a relation to the group of five-toothed Argentine 

 Spixias similar to that of typical 0. janeirensis in comparison with 

 0. punctatissimus. It is merely a species in which the apertural 

 folds and lamellae have degenerated, as in O.patagonicus of the same 

 region. My description of this species under a new name was due 

 to the original generic reference. It is totally unlike Eudioptus. 



A specimen from Golfo Nuevo, some distance down the coast from 

 Bahia Blanca, is yellowish-green, with faintly darker streaks, and is 

 costulate-striate (pi. 11, fig. 58). 



Figs. 56, 57, are from Doering's illustrations. Fig. 59 shows one 

 of the types of the synonymous stearnsianus^ from the Sierra 

 Ventana. 



Subgenus PLAGIODONTES Doering, 1876. 



Plagiodontes DOER., Boletin de la Academia Nacional de Cien- 

 cias, ii, p. 318; Cordoba, 1876; type, dentatus Wood; Periodico 

 Zoologico ii, pt. 4, p. 237 (1877). 



Shell rimate, ovate or oblong, corneous or brown, with 6^-8 com- 

 pactly coiled whorls, the first 1^ having dense waved striae or 

 straight riblets; last whorl large, scarcely pitted behind the lip ex- 

 cept at the base. Aperture subvertical, truncate-ovate, obstructed 

 by 3 principal lamellae and folds, and a variable number, 0-5, of 



