Mat, 1893.] MOLLUSKS OF THE DEATH VALLEY EXPEDITION. 281 



Nelson, Bailey, and Orcutt collected living examples, but places still 

 farther north, in the Great Basin so-called; for certain forms collected 

 by Dr. Yarrow* in 1872 on the shores of Sevier Lake, middle Utah, 

 though unfortunately few in number and somewhat weathered, were 

 regarded by the late Mr. Tryon, to whom the specimens were sub- 

 mitted, as -"a representative of the genus Tryonia," and are referable 

 to no other form. (Mus. No. 739G0.) 



In course of time living specimens from new localities may come to 

 our knowledge, as they have within the past five years, since Orcutt 

 led the way with his Indian Springs collection, and it may be found, 

 that in springs where the water is comparatively permanent in volume 

 and sweet, the smooth form prevails, and vice versa, so far as quantity 

 and quality of water and the matter of shell characters. Information 

 on these points is now what is wanted. 



Tryonia clathrata Stimpson. 



Pahranagat Valley, Nevada (Mus. No. 123,621), Dr. C. Hart Merriam, May 25, 1891. 



This is the veritable form described by the late Dr. William Stimpson 

 in February, 1865, from the dead bleached specimens collected by Prof. 

 William P. Blake on the surface of the Colorado Desert, while con- 

 nected with one of the Pacific Eailroad surveys, nearly forty years ago. 

 Prof. Blake found it together with other small fresh- water gastropod 

 shells, including Gould's Amnicola protea. Subsequently Gen. Carl- 

 ton collected several examples of T. clathrata while on his way east with 

 his command in 1861-'62, but in neither case is the exact locality of 

 Blake's or Carlton's specimens stated. In neither of the lots collected 

 by them were there any living examples; all were of a porcelaneous 

 whiteness, the same as the innumerable bleached specimens of the more 

 common protea-exigua form, that are spread over the surface of the 

 desert. Of the thousands of these latter that I have received and col- 

 lected along the line of the Southern Pacific Eailroad, not a single ex- 

 ample of clathrata has rewarded me for the time expended in the effort 

 to find a specimen by the subsequent examination of the material from 

 this part of the desert. Dr. Merriam's find indicates a more easterly 

 and less southerly distribution for clathrata, and quite likely it may 

 prove to be less abundant than its ally. Dr. Merriam's examples were 

 found in a hot spring; the temperature of the water as noted being 

 97° F. 



Pluminicola fusca Hald. 



Kelton, Utah Territory (Mas. No. 123623), Vernon Bailey, November 7, 1891. 



Five semifossilized examples were detected in the dry wash of a clay 

 bank at an elevation of about 100 feet above the lake. 



Fluminicola merriami Pilsbry and Beecher. t 



"Shell small, globose turbinate, narrowly but distinctly and deeply 

 umbilicated. Spire low-conic, acute; whorls four, slightly shouldered 



*U. S. Geol. Survey, W. of the 100th Meridian, vol. V, p. 948. 

 tThe Nautilus, vol. v, April 1892, p. 143. 



