556 PATAGONIAN EXPEDITIONS : ZOOLOGY. 



Springs along the Rio Chico de la Sta. Cruz, at the following places : 

 About 15-20 miles above the mouth of the Rio Chalia; springs 20 and 

 25 miles below the Sierra Ventana ; spring near the Sierra Ventana (type 

 locality) ; 25 and 50 miles above the Sierra Oveja. Also near Mt. of 

 Observation, on the coast, below the mouth of the Santa Cruz River. 

 Also at the foot of the Andes, 50 miles north of the Rio Chico. 



This species resembles several forms of the Rio de La Plata system, but 

 is distinguished by the combination of quite strongly convex whorls and 

 a continuous peristome ; its inner margin, though not much thickened, yet 

 forms a distinct ledge across the preceding whorl. The striation is exag- 

 gerated in fig. 9, and the umbilical chink is represented too wide and 

 prominent in both figures. The apex is reddish in the type lot, but not 

 in others. L. simplex occurs in the same springs with L. hatcheri along 

 the Rio Chico, but it is apparently less abundant and it does not seem to 

 ascend the river so far. 



LlTTORIDINA SUBLINEATA Sp. nOV. 

 (Plate XLVI*. Figs. 5, 5*.) 



The shell is imperforate, ovate-pyramidal, thin, light brown. Surface 

 faintly marked with growth-lines, and on the last half of the last whorl 

 there are several (four or five in the type specimen) very low spiral cords, 

 grouped in the peripheral region. The spire is rather straightly conic, 

 the summit a little obtuse, the apex rising but little above the level of the 

 first whorl. Whorls 5, convex, the last very indistinctly angular below 

 the periphery, causing the base to appear slightly flattened. The aperture 

 is ovate, very slightly oblique; peristome thin and acute, the outer margin 

 not darkened or thickened. Columella concave, slightly thickened, con- 

 tinued in a thin adnate callus across the parietal wall. 



Length 3.6, diam. 2.2 mm., length of aperture 1.5 mm. 



Small stream on the Rio Chico, 35 miles above the Sierra Oveja (type 

 locality) ; also in a spring 25 miles above the Sierra Oveja, and in a "big 

 spring on the Rio Chico," the exact location of which was not noted on 

 the collector's label. 



It sometimes attains a larger size than the type, a shell from the second 

 lot noted above being 5.4 mm. long with 5^ whorls. This species differs 

 from L. simplex by its weakly subangular periphery, marked with a few 

 spiral lines, the less prominent parietal callus and fragile outer lip. 



