562 PATAGONIAN EXPEDITIONS I ZOOLOGY. 



Malak. Blatter, n. R, I, 1879, p. 153, Taf. 8, f. 3. 7X3-4 mm., 



whorls 6. Guayaquil River, Guayaquil, Ecuador. 

 LITTORIDINA BOETZKESI (Miller). Pciludestrina boetzkesi Miller, t. c., p. 



155, Taf. 8, fig. 4. 4.5 X 2.4 mm., whorls 6 l / 2 . S. Domingo and 



Guayaquil River, Ecuador. Cf. L. guadichaudii. 

 LITTORIDINA (?) PEDRINA (Miller). Hydrobia pedrina Miller, t. c., p. 155, 



Taf. 6, f. 7. 3.5 X 1.5 to 4X 1.8 mm., 5^ to 5% whorls. Micro- 



scopically granulose. Rio Pedro in the Chillo valley, Ecuador. 



POTAMOPYRGUS Stimpson. 



Potamopyrgus Stimpson, American Journal of Conchology, I, 1865, p. 53; 



Researches upon the Hydrobiinae, Smiths. Misc. Coll. No. 201, p. 49. 



Monotypic ; type, Melania corolla Gld. 

 Lyrodes Doering, Bol. Acad. Nac. Ciencias Cordoba, VII, 1884, p. 461. 



Type L. guaranitica. 

 Pyrgophortis Ancey, Bulletin de la Societe Malocologique de France, V, 



1888, p. 192. Type, Pyrgulopsis spinosa C. & P. 

 Huttonia Johnson, Proc. Royal Society of Tasmania for 1890, p. 90 



(1891). Type, Potamopyrgus corolla. 



Amnicolinae with rather slender, thin, rimate shells of ovate-conic or 

 turrited contour, often armed with a row of spines on a delicate keel at 

 the shoulder of the last whorl or two. They differ from other American 

 genera in being viviparous. 



Besides the following species, P. coronatus Pfr. is known from Baran- 

 quilla, Colombia, and Lake Valencia, Venezula. It has a wide range in 

 Mexico and the West Indies. Professor von Martens has figured the 

 shell, teeth and embryonic young. (Die Binnenmollusken Venezuelas, 

 p. 208, Taf. 2, figs, 



POTAMOPYRGUS GUARANITICUS (Doering). 



Lyrodes guaranitica Doering, Boletin de la Academia Nacional de Cien- 

 cias en C6rdoba (Republica Argentina), VII, 1884, pp. 461-463, fig. 2. 



Length 3.5, diam. 1.9 mm., whorls 5^ , the last encircled by a slender 

 keel at the shoulder, and several spiral striae on the base. 



Rio Barrancas, Corrientes. 



