528 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



and more or less malleation. One measures, length 14, diam. 8, length 

 of aperture 8.6 mm.; whorls 4^. Those from the Arroyo Eke, near the 

 head of Spring Creek, are also small. 



In Swan Lake (about 50 miles north of the Rio Chico) the shells are 

 very delicate, almost like tissue paper, but little malleated or (usually) 

 without malleation, and of a pale olive color. Most of the examples con- 

 form nearly to PI. XLVI(7, fig. 2, in shape, but I have also figured the most 

 elongate (fig. i) and the shortest (fig. 3) shells. Fig. 2 measures, length 

 19, diam. 11, length of aperture 10.9 mm.; whorls 4^. 



Mr. Hatcher in his narrative has alluded to the abundance of shells in 

 this lake (Reports of the Princeton University Expeditions to Patagonia, 

 I, p. 166). The lake basin is composed of igneous rocks dammed by a 

 lava flow. To the absence of calcareous material, the tenuity of the shells 

 is probably due. 



Lymncca byimneojlavida Preston, Annals and Magazine of Natural His- 

 tory (8), V, January, 1910, p. no, pi. 4, fig. i, from the Falkland Islands, 

 is described as wider, more opaque and darker than L. diaphatia, alt. 14, 

 diam. 8, aperture 8.75 mm. It evidently stands close to L. diapluma. 



Lymn^a patagonica Strebel. 



Limncea patagonica Strebel, Zool. Jahrb., XXV, p. 164, Taf. 8, figs, lo-^a, 

 b, 1907. 

 Strebel's types are said to differ from the form he describes as L. 

 diaphana by being browner, more of a chestnut-brown, the whorls in- 

 crease more rapidly in width, the apex is commonly broken, with the 

 breach closed by shell-material ; the columella stands more nearly vertical, 

 and its reflection is somewhat wider, but leaves an umbilical crevice open. 

 It measures as follows : 



Length 14.8, diam. 12.6, aperture 10.7x6.8 mm., 3^ whorls remaining. 

 10.4, " 8.1, " 7.2x4.5 " 3 



Puerto Bridges, in a fresh-water lake. 



Lymn^a patagonica riochicoensis subsp. nov. 



(Plate XLVI, Figs. lO, ii.) 



The shell resembles L. patagonica in shape, being short ovate ; the axis 

 is imperfoyate. It is pale Jioney-yellow or very pale yellowish-brown. In 



