WHITE. ] LARAMIE FOSSILS. 95 
from the obsolescence of the vertical cost on the lower part of the last 
turn, become more or less continuous revolving lines on that part of the 
shell. 
‘« The specimens of this species yet obtained are too imperfect to af- 
ford the means of giving accurate measurements. Judging, however, 
from some of those in the collection, large adult individuals would seem 
to have attained a length of 1.40 inches, with a breadth of body volu- 
tion of near 0.50 inch. Some of these larger specimens, consisting 
of three or four of the lower volutions, show but a very gradual de- 
crease in breadth upward; while some of those composed of the upper 
part of the shell indicate a divergence of about 18° for the angle of that 
portion of the spire. 
“As none of the specimens show the aperture, it is not possible to de- 
termine from those yet seen whether this shell really belongs to the 
fresh-water genus Goniobasis or to some marine genus, although the spe- 
cies will be readily recognized by its seulpturing. Its only known as- 
sociates are fragments of Ostrea and Modiola, with Corbula undifera, an 
association that would certainly favor the conclusion that it should be 
referred to a marine genus, in which case it would most probably fall 
into Bittium, and have to be called B. insculpta. 
‘¢ We have, however, several examples of unquestionable fresh-water 
Shells associated with marine types in some of the rocks of this region ; 
while the general aspect of this shell seems, as far as known, to asso- 
ciate it with Goniobasis. The fact, too, that nearly all the specimens yet 
seen are fragmentary, seems to indicate that the species did not live in 
the same waters with the other forms found associated with it, but that 
the specimens may have been washed into the sea from streams on the 
neighboring shores. 
‘“¢ Locality and position.—Rock Springs, Wyoming; from a little above 
the main 10-foot bed of coal at that locality. Bitter Creek series.” 
While this shell is almost certainly a fresh-water form, there is no 
positively known reason for referring it to the genus Melania proper. It 
is, however, almost certainly genetically related to the next described 
species, as I suggested in the report of this survey for 1877; and in view 
of the form and ornamentation of the species referred to, I prefer at 
present to retain it with that species in the genus Melania; and this 
form being so related to that one, both seem to require the same generic 
assignment. 
MELANIA WYOMINGENSIS Meek. 
Plate 28, figs. 6 a and b. 
Melania (Goniobasis?) wyomingensis Meek, 1873, An. Rep. U. 8S. Geol. Sur. for 1872, p. 
516. 
Melania larunda White, 1876, Powell’s Rep. Geol. Uinta Mts., p. 131. 
Shell large, elongate; volutions apparently eleven or twelve, uniformly 
increasing in size, moderately convex, the last five or six of them bear- 
ing about the middle or a little above it a revolving row of prominent, 
strong, outward-projecting, laterally compressed and somewhat sharp- 
ened tubercles. These tubercles are strongest upon the last volution and 
gradually diminish in size until they disappear among the crenulated 
lines that mark the volutions of the spire. They decrease in number 
also, there being about fifteen on the last volution, and about ten on that 
upon which they first appear. The upper volutions of the spire are 
marked by numerous crenulated longitudinal varices having a slight 
convex curve to the left side of the shell, the crenulations being caused 
