8 
in several details of ornamentation. The new species lacks the short, 
transverse ridges which in U. holmesianus are “nearly at right angles 
to the lines on the front of the shell”. It also lacks the thread-like, raised 
lines which in White's species run from the beak down the crest of the 
umbonal ridge. In U. mclearni the V-shaped sinuses of ornamentation 
reach to the beak and are not preceded by the sharp, slightly undulating, 
concentric ridges nearly parallel with the growth lines. Still another 
difference is that in U. holmesianus the apex of the deepest sinus of orna- 
mentation is in the broad umbonal furrow, whereas in the new species 
it lies in front of the furrow. 
Dimensions of Type (a slightly distorted form). Length, 34 mm.; 
height, 29 mm,; thickness, about 22 mm. 
Unio humei sp. nov. 
Plate IV, figures 1 and 4 
In the collections made by T. C. Weston in 1888 from Fossil coulee 
(about secs. 7 and 8, tp. 4, range 19, W. 4th mer.) there are certain specimens 
of Unio which in form resemble the marine shell Arctica ovata. 
The shell is transversely ovate, moderately convex, and the valves 
quite thick; the anterior extremity evenly rounded, but the posterior 
extremity narrowly rounded; basal margin semi-oval; the posterior dorsal 
part of the type is partly broken away, but other specimens show it to be gently 
convex, the anterior dorsal margin is somewhat more abruptly rounded; 
beaks moderately elevated and located midway in the anterior third of 
the shell. Internally the shell is quite thick and heavy; the lateral teeth 
have not been seen and the smaller of the cardinal teeth is not well pre- 
served; the cardinal tooth which is preserved is large. 
It is rather close to the form, referred doubtfully to Unio pyramida- 
toides by Stanton^, from the Fruitland formation of New Mexico, but 
is longer in proportion to height and the posterior margin is not truncated. 
Dimensions of Type. Length, 78 mm.; height, 64 mm. 
Horizon and Locality of Type. Pale beds; Fossil coul4e (about sec. 17, 
tp. 4, range 19, W. 4th mer.). 
GASTEROPODA 
Viviparus crickmayi sp. nov. 
Plate III, figure 3 
This species differs from V. tasgina, the most closely related form, 
chiefly in the greater prominence of the shoulder on the upper part of the 
whorl. 
The lower two-thirds of the body whorl is evenly rounded, but on 
its upper part there is a shallow, revolving depression surmounted by a 
moderately prominent, rounded ridge. Above the ridge the outline of 
the whorl turns in abruptly almost at right angles to the axis of the shell 
to form the shoulder. In many cases the shoulder is 3 mm. wide. It is 
usually quite flat, but occasionally slightly concave. Proceeding toward 
‘Stanton, T. W.: U.S. Geol. Surv., Prof. Paper 98, p. 309 et seq. (1916). 
