PILSBRY: non-marine MOLLUSCA of PATAGONIA. 559 



LiTTORIDINA BERTONIANA Sp. nOV. 

 (Plate XLlc, Fig. 9.) 



The shell is barely perforate, oblong-turrite, pale olivaceous, the length 

 about double the greatest diameter, and two and one-half times the length 

 of the aperture. Spire rather straightly conic, the apex obtuse. Whorls 

 5^ , moderately convex, the last well rounded. Surface delicately marked 

 with very fine spiral stride, usually strongest on the penultimate whorl. 

 The aperture is ovate, angular above. Peristome thin and simple, contin- 

 " uous, the columellar margin narrowly expanded. 



Length 3.6, diam. 1.7, length of aperture 1.4 mm. 



Puerto Bertoni, Paraguay. Types No. 103,045, A. N. S. Phila., from No. 

 244 of the Museu Paulista, collected by A. de W. Bertoni. 



This species differs from Potamopyygus peteniugensis (Gld.) by its much 

 less convex whorls, smaller size and minute spiral striae. Potamopyrgiis 

 scottii has far more convex whorls and coarser sculpture. 



In some specimens from the type locality the spiral striae are extremely 

 minute and weak, yet visible under the compound microscope. These 

 were sent under No. 190 Museu Paulista. 



A few other species at present referred to Litioridina, such as L. pedrina 

 Miller, have spiral sculpture ; yet the presence of this unusual feature raises 

 some doubt as to the genus, which can be definitely determined only by 

 examination of the genitalia. L. bertoniana may prove to belong to 

 Potamopyygus. 



Other species of Littoridina described from South America, 



SOUTH OF the Equator.^ 



Littoridina isabelleana (d'Orbigny). Palndestyina isabelleana d'Orb., 

 Voy., p. 385, pi. 75, figs. 4-6. 3 X I mm., whorls 6, flat. In a stream 

 near Montevideo and in the Bay of Montevideo at the contact of fresh 

 and salt water. 



Littoridina parchappii (d'Orbigny). Palitdiua paychappii d'Orb., t. c, 

 p. 30; Palndestyina paychappii d'Orb., Voy., p. 383, pi. 48, figs. 1-3. 

 6.5 X 3 mm. with 7 very convex whorls ; whitish, aperture not angu- 



' This list is believed to be a complete catalogue of the genus up to the end of 1909. Palu- 

 dina brunnea and P. conica Anton, Verzeichniss, 1839, p. 52, South America, and Bulimus palu- 

 dinoides. Ibid., p. 42, are probably Littoridina;, but the descriptions are totally inadequate and 

 the names should be deleted from the list of species. 



