1906. ] NATURAL SCIENCES OF PHILADELPHIA. 173 
whorl at the aperture shows it to be adult. Five specimens were taken. 
The shells are all more or less bleached, the freshest being of a pale 
corneous tint. The round whorls, deep suture and general appear- 
ance are quite unlike any Planorbis or Vallonia, and indicate, we think, 
either that it is a Valvata or an Amnicoloid snail comparable to Horatia 
Bet. or Daudebardiella Bttg. in the Palearctic fauna. Until fresh 
specimens with the soft parts or operculum are found, the position of 
this molluscan atom will remain uncertain. 
Valvata micra nugax (pl. IX, fig. 6), a slightly larger form, alt. .9 
diam. 1.5 mm., with three whorls and a projecting spire, may prove to 
be a distinct species; but for the present, until more specimens are 
found, it may be placed under V. micra as a variety or form. 
CYRENIDA. 
Pisidium singleyi Sterki. 
Nautilus, XI, 1898, p. 112 (type loc. Guadalupe river, Comal county, Texas). 
Drift débris of Guadalupe river about four miles above New Braun- 
fels, and of Devil’s river, Val Verde county, Texas. A closely related 
form was found near Del Rio. 
Pisidium compressum Prime. 
New Braunfels, Comal county, Texas. Mr. J. A. Singley found P. 
trapezoidewm Sterki at the same place (coll. A. N.S. Phila. No. 60,127). 
Pisidium abditum huachucanum nN. subsp. 
The shell is quite inflated, dark brownish-olive, irregularly striate 
and marked with several conspicuous dark growth-arrest streaks; 
very inequilateral, the beaks low and near the anterior end. Anterior 
end abruptly truncate, posterior end produced and rounded. Hinge 
rather narrow, the lateral teeth in the right valve single, short and 
high, triangular;in the left double. Length 5.1, alt. 4.8, diam. 3.4 mm. 
Stream in Carr canyon, Reef, Cochise county, Arizona, collected by 
C. R. Biedermann, February 8, 1904. 
Specimens were submitted to Dr. V. Sterki, who could not identify 
the form with any known species. About half of the shells are more 
compressed than those described as typical, one measuring, length 4.1, 
alt. 3.4,diam.2 mm. The very inequilateral, anteriorly truncate out- 
line and low beaks are characteristic of both the obese and com- 
pressed forms. 
Eupera singleyi (Pils.). 
Spherium (Limosina) singleyi Pils., Proc. A. N.S. Phila., 1889, p. 88, pl. 
3, figs. 14, 15 (May 14, 1889). 
? Cyclas maculata Morelet, 1859, not of Anton, 1839 =Spherium yacatunense 
Fischer and Crosse, Miss. Sci. Mex., Moll., II, p. 653 (1894). 
This species is now known to us by specimens from the following 
