276 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
widel}' distributed in the course of exchanges between conchologists 
as Tryonla ; the latter genus is based on external or shell characters 
only, and upon these characters is readily separable from any of the 
numerous varieties of the much commoner form illustrated herein. 
From Flowing Springs, many miles from the railway and the station 
known by said name, I haye received probably over a thousand exam- 
ples of PaludestTma since the major portion of this paper was 
written \ 
The species assigned to the first of these genera which exhibits the 
numerous varietal aspects figured below, as well as certain other forms 
hereinafter mentioned, was first detected by Prof, William P. Blake '^ 
and Dr. Thomas H. Webb. It was described by Dr. A. A. Gould in 
March, 1855, as Amnlcola iwotea^ and by T. A. Conrad as Melania 
exigua, in Februar}^, 1855. Gould's description was published first, 
therefore his name has precedence. Binney placed it in Stimpson's 
genus Tryonla, which error has been continued by subsequent authors, 
including the writer, who removed it in 1893 to Bythinella. 
As the numbers of the Smithsonian publications containing Binney's 
Land and Fresh-water Shells of North America are out of print, and 
the original descriptions are accessible only to a small number of stu- 
dents, I have quoted Gould and Conrad as below from Binney.^ 
AMNICOLA PROTEA Gould. 
Shell elongate, slender, variable; whirls seven to eight, rounded, divided by a 
deep suture, simple or variously ornamented, and barred with revolving ridges and 
longitudinal folds; aperture ovate; lip continuous, simple, scarcely touching the 
penultimate whirl. Length of the largest specimen, three- 
tenths, breadth, one-tenth inch. 
From the Colorado Desert (Gran Jornada), Dr. T. H. 
Webb, W. P. Blake. 
Peculiar from its large size and slender form, though 
differing greatly in its relative proportions. It differs from 
all others in being variously sculptured with revolving 
Fig. 1.— AMNICOLA protea. ridges and longitudinal folds, like most Melnui.r. It varies 
greatly also in the relative proportions of length and 
breadth. It is as slender as Amnlcola attemmte Hald., and much larger. This appears 
to be the same shell as that subsequently descrilied by Mr. Conrad, under the name 
of Melania exigua. (Gould. ) 
MELANIA EXIGUA Conrad, 
Turreted; volutions eight, disposed to be angulated and somewhat scalariform 
above, cancellated, longitudinal lines wanting on the lower half of the body whirl; 
' The great canal system of the Imperial Company by which the waters of the 
Colorado River are in part diverted so as to irrigate hundreds of square miles of the 
desert is rapidly approaching completion. The water is already flowing in a consider- 
able portion of the system and soon a part of the sandy waste will give place to green 
and fertile fields, forming an oasis in the midst of the arid desert. 
'' Pacific Railroad Reports, V, 1857, p. 332. 
=* Part III, p. 70 (Tryonia). 
