PILSBRY: non-marine MOLLUSCA of PATAGONIA. 565 



Unfortunately Lan::aia and Pterides are known by dead and bleached 

 shells only, so that the relationship suggested remains hypothetical. It 

 affords no safe basis for deductions concerning the antecedents of the three 

 groups, each known from a single spot, and separated from its supposed 

 relatives by thousands of miles. 



The genera are characterized as follows : 



Common characters : — Shell turrite, composed of very convex whorls ; aperture strongly 

 diagonal to the axis of the shell, oval, the posterior end rounded, spreading or sinused, 

 the basal margin also retracted or effuse ; peristome continuous, more or less expanding, 

 running forward below. 



a. Shell openly umbilicate, thin, sculptured with sinuous longitudinal ribs and fine spiral 



stria, minute (2 to 3 mm. long, with 6 whorls) ; the aperture elliptical, lip broadly 

 flaring. Dalmatia. Lanzaia Brusina. 



b. Shell rimate, thin, smooth, minute (2.5 to 3 mm. long, with 7 to 10 whorls) ; the aperture 



ovate ; lip sinused or spreading above, broadly retracted or spreading at the base. 

 Mexico. Pterides Pilsbry. 



c. Shell perforate, solid, smooth, of about 7^ whorls; the aperture oval, small, the lip 



having a rounded sinus above and a smaller one at junction of outer and basal margins, 

 which expand but little. Southeastern Brazil. Idiopyrgus Pilsbry. 



Idiopyrgus souleyetianus sp. nov. 



(Plate XLIc, Figs. 14, 14a.) 



The shell is perforate, solid, turrited, greenish-yellow, opaque. The 

 surface is smooth and glossy, growth-lines very faint. The spire tapers 

 regularly to a small but obtuse apex. Whorls 7>^ , all strongly convex, 

 joined by deep sutures. The aperture is oval, oblique, the basal ni-argiti 

 being advanced, the outer lip retracting upward. The peristome is con- 

 tinuous, the outer lip expanded, somewhat thickened within. It has a 

 rounded sinus just below the upper insertion, and a small sinus at the junc- 

 tion of the outer and basal margins. The continuous columellar and 

 parietal margins are arcuate, forming a raised ledge across the parietal wall. 



Length 5.3, diam. 2.1 mm., length of aperture with peristome 1.9 mm. 



Rio Doge, State of Espirito Santo, Brazil. Types No. 100,534, A. N. 

 S. Phila., from No. 127 Museu Paulista. 



In old individuals the spire becomes more or less shortened by erosion 

 of the early whorls. This form differs from the Littoridinas by its peculiar 

 peristome. It is probably a straggler from the fauna of eastern Brazil, of 

 which little is yet known. 



