LYMNEZIDA OF NORTH AMERICA. 8Y 
B. DESCRIPTIONS OF AMERICAN FOSSIL LYMNAAS. 
COMANCHEAN LYMNAEAS, 
Galba ativuncula (White). Plate XVI, figures 1, 2. 
Limnea ativuncula Wuite, Bull. U. S. Geol. Surv., no. 29, p. 20, pl. 4, 
figs. 10-11, 1886; Proc. Amer. A. A. Sci., XXXIV, p. 241, 1890; Bull. U. S. 
Geol. Surv., no. 128, p. 71, 1895—Boy.e, Bull. U. S. Geol. Surv., no. 102, p. 167, 
1893.—ScHUuCHERT, Bull. U. S. Nat. Mus., no. 53, i, p. 355, 1905. 
“SHELL small, spire moderately slender; volutions about six in 
number, convex, the last one enlarged and somewhat longer than the 
spire. Surface marked by the usual lines of growth. 
“Length of the largest example in the collection, 8 millimeters; 
but their average length is considerably less” (White). 
Type: U.S. Nat. Mus. no. 20054. 
Horizon: Atlantosaurus beds, Comanchean Period. 
Locatity: Eight miles north of Canyon City, Fremont County, 
Colorado. 
Remarks: “The younger examples of this species are more slen- 
der than the adult specimens on account of the proportionally greater 
enlargement of the last volution upon reaching maturity. These younger 
examples are so slender as to suggest their reference to Acella, but 
the older shells have more the shape of true Limnza” (White). 
From the figures, this species most nearly resembles certain recent 
Lymnezas which Lea described as rustica. It certainly falls in the group 
with obrussa, rustica, plica and parva, and could scarcely be distin- 
guished from certain individuals of these species had the specimens 
the fresh appearance of recent shells. Occurring as it does in the 
oldest strata from which American Lymnzas have been secured, the 
parallel in resemblance is all the more remarkable, showing clearly, 
as remarked by Dr. White, that the Lymnzid fauna was well estab- 
lished at this period. 
Galba consortis (White). Plate XVI, figures 3, 4. 
Limnea consortis Wuite, Bull. U. S. Geol. Surv., no. 29, p. 20, pl. 4, figs. 
8-9, 1886; Bull. U. S. Geol. Surv., no. 128, p. 71, 1895.—Boy Le, Bull. U. S. Geol. 
Surv., no. 102, p. 167, 1893—ScHucHERT, Bull. U. S. Nat. Mus., 53, i, p. 356, 
1905. 
“SHELL moderately small; spire short; volutions about five. in 
number, convex, the last one inflated and much longer than the spire. 
Surface marked by the usual lines of growth. Ee 
“Length of largest example, 10 miilimeters; breadth of the last 
volution, 5 millimeters” (White). 
1Amer. Journ. Sci., iii, vol. XX, p. 44. 
