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 thia ; columella oblique but foldleas. 



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 O.Janeirensis in comparison with 

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

 folds and lamellae have degenerated, as in 0. 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 strise 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 



