554 PATAGONIAN EXPEDITIONS I ZOOLOGY. 



The last whorl is rounded and expands towards the aperture, at the upper 

 angle of which it descends slightly. The aperture is subvertical, sym- 

 metrically ovate, narrower but not angular above. The peristome is con- 

 tinuous, of a deep reddish brown color, almost black at the edge. The 

 outer margin is slightly thickened and obtuse ; the inner margin is rather 

 heavily calloused, forming a raised ledge across the preceding whorl, 

 from which it is slightly detached above and below. 



Length 2.25, diam. 1.2 mm.; length of aperture i.i mm. (PI. XLII, figs. 



7, 7)- 



Rio Chico de la Sta. Cruz, Territory of Santa Cruz, Argentina, from 



below the mouth of the Rio Chalia to the mouth of the Rio Belgrano ; 

 and northward along the eastern slope of the Andes 65 miles, in springs 

 and small streams. Specimens were taken at the following localities : 

 Spring on the Rio Chico below the mouth of the Rio Chalia (2 : 12 : '99) ; 

 spring on Rio Chico, 25 miles below Sierra Ventana (type locality) ; 

 twenty miles below Sierra Ventana, in a spring ; north side of Rio Chico 

 near Sierra Ventana ; Rio Chico, 40 miles above Sierra Ventana ; small 

 stream 5 miles above Sierra Oveja ; small stream on south side of Rio 

 Chico, 50 miles above Sierra Oveja ; near the mouth of Rio Belgrano ; Rio 

 Blanco, base of the Andes ; spring 50 miles north of Rio Chico, elevation 

 1750 ft; spring near base of the Andes, 65 miles north of the Rio Chico, 

 elevation 2400 ft. Also several lots from springs on the Rio Chico with- 

 out exact location. 



This small snail is evidently abundant in springs and small streams 

 along the whole course of the Rio Chico de la Sta. Cruz. It is apparently 

 related to L. kuesteri and especially to L. k. cordillercz (Strobel), 1 from the 

 Province of Mendoza, but differs from these by its wider, convexly conic 

 spire, the shape of L. hatcJieri being rather pupiform, whereas the spire is 

 strictly conic in L. kuesteri and cordillerce. 



L. hatcheri varies within wide limits in nearly all of the colonies col- 

 lected. This variation is chiefly ( i ) in size, nearly every lot consisting of 

 both large and small individuals, the difference being greater than I have 

 ever observed in North American Amnicolidce ; and (2) in the degree 

 of descent, lateral deviation or uncoiling of the last whorl. As type I 

 have selected a shell nearly normal in shape, PI. XLII, figs. 7, ja, 2.25 



1 Hydrobia kusteri and var. cordillera Strobel, Materiali per una Malacostatica di Terra e di 

 Acqua dolce dell'Argentinia Meridionale, p. 61. Pisa, 1874. 



