ODONTOSTOMUS. 95 



(1874) Towigerus dentatus MORCII, Catal. Yoldi, p. 29. Odontos- 



tomus dentalus DOKKJX;, lioi. Arad. Nac. Ciencias, Cordoba, 1875, 

 p. 452; Periodico Zoologico i, pt. 3, j). 197 (1875). Plagiodontes 

 dentalus DOER., Bol. Acad. Cord, ii, p. 318 ; Periodico Zoologico ii, 

 pt. 4, p. 238 (1877). i?. (Plagiodontes} dentatus KOB., Jahrb. 1878, 

 p. 133. Pupa dentata DESH. in Fer., Hist., p. 218, pi. 1G2, f. 17, 

 18 Helix sowerbiana FER., Prodr., p. 71, no. 492 bis (nude name). 

 ORBIGNY, Mag. de Zool., 1835, p. 22. Cyclodontina sowerbyana 

 BECK, Index, p. 88 Pupa sowerbiana ORB., Voy., p. 321, pi. 41 

 bis, f. 15, 16 (exclusive of var. patagonica} POT. et MICH., Galerie 

 i, p. 173, pi. 17, f. 7, 8. Odoiitostomus (Plagiodontes} sowerbyamis 

 Orb., ANCEY, Le Naturaliste, May, 1901, p. 103. Pupa labyrinthus 

 in Berlin Museum, ANTON, Verzeichniss, p. 47, no. 1749 (according 

 to Pfr.); nude name. 



In most of the specimens from Montevideo the fold lying between 

 the basal and lower palatal is wanting, as it was in Wood's type ; 

 but it is sometimes present or even represented by two folds. It 

 occurs in specimens from Colonia and Entre Rios. Ancey mentions 

 that in one specimen he found five irregularly placed denticles 

 within the basal lip. 



In the Montevideo shells the upper end of the composite parietal 

 lamella, or that part representing the angular lamella, is usually a 

 mere low buttress on the right side of the true parietal (fig. 15), but 

 in some specimens from other localities it is more tubercular, and a 

 low callous cord runs upward from it to near the termination of the 

 outer lip. In immature specimens of 0. dentatus at a^ certain stage 

 the components of the parietal lamella stand separate upon the 

 parietal wall (pi. 15, fig. 33). 



O. PATAGONICUS (Orbigny). PI. 14, figs. 20-24. 



Shell deeply rimate, pupiform with conic spire, rather solid, light 

 olivaceous brownish with darker longitudinal streaks; somewhat 

 shining, sculptured with fine, irregular growth-stria?. Last whorl 

 subcylindrical or barrel-shaped, those above rapidly tapering, form- 

 ing a rather short, conic spire. Whorls 6 or 7, nearly flat, the last 

 with a more or less distinct basal keel on its latter half, and having 

 a small flattened tract within the keel behind the basal lip. Aper- 

 ture vertical, shortly, irregularly ovate, obstructed by three principal 

 lamella? and one or two smaller denticles or teeth : one curved 



