May, 1893.] MOLLTJSKS OF .THE DEATH VALLEY EXPEDITION. 279 



surrounded and shaded by tules. The water is warm ; in Mr. Orcutt's 

 judgment not under 100° P., and tastes like the water of the Dos Pal- 

 mas Spring - , 6 miles north of Salton on the opposite side of the desert, at 

 the base of the Ohuckawalla or Lizard Mountains. "An analysis of the 

 Dos Palmas Spring water gives slight traces of alum , soda and sulphur and 

 shows that considerable salt is held in solution, but it is not too salt for 

 use. These springs are all below the present sea level about 100 feet, 

 judging from the fact that Salton lying in the depression between 

 Dos Palmas and Indian Springs, is reported to be 250 feet below sea 

 level from actual measurements." Specimens from this place kindly 

 presented by Mr. Orcutt* are contained in the National Museum (No. 

 104886). 



Mr. Pilsbry remarks as to B. seemani, " it is indeed much like a 

 smooth Tryonia. I wonder whether the Tryonias are not simply 

 examples of this, isolated in a gradually evaporating basin, becoming 

 more and more saline ! However this may be, the shells you submitted 

 to me for my determination are the real seemani. 1 ' 1 



Gould's n&meprotea is eminently appropriate; besides the smooth 

 form herein discussed and inclusively regarded as the same as Prauen- 

 feld's, and Orcutt's Indian Springs granulose examples, we find other 

 varietal aspects and the sculpture varying between faint or barely dis- 

 cernible, to moderately defined or conspicuous. Sometimes the shells 

 are shouldered or angulated on the upper side of the whorls, often trav- 

 ersed spirally by slender lirse or threads, and these again modified by 

 longitudinal ribs or costae. And the proportions of the shells in shape 

 also vary exceedingly; sometimes drawn out, elongated, attenuated, 

 and slender, again short and robust. The mouth smaller or larger; 

 the whorls varying in convexity and all of these aspects of sculpture 

 and form, are seen, when hundreds of specimens are examined, to inter- 

 grade or bjend together in a greater or less degree. Occasionally 

 there is an example that hints of Stimpson's elathrata, but I have not 

 thus far been able to connect the two forms. Again referring to Mr. 

 Pilsbry's note, writing of seemani he says "it is no doubt a Bythinellaf 

 related quite closely to our nidkliniana.' 11 



Without here considering the niceties of generic distinction between 

 HydroMa% (in which Frauenfeld placed his species seemani), and 

 BytMnella, it will readily occur to the reader, that a form so variable, 

 would be likely in some phase of its variation to closely approach it 

 not absolutely and inseparably resemble individuals of other species 

 belonging to more or less intimately related, though geographically 

 widely separated groups. . 



*See Orcutt's notes in West American Scientist, September, 1888, and May, 1889. 



t Agreeing with Mr. Pilsbry on this point, it will be seen that I have adopted the 

 generic name, BytMnella, for Dr. Gould's species. 



tVide Stimpson's Researches upon the Hydrobiinre, etc., Smithsonian Misc. Coll., 

 201, August, 1865. 



