WHITE. LARAMIE FOSSILS. 71 
UNIO SUBSPATULATUS Meek & Hayden. 
UNIO DEWEYANUS Meek & Hayden. 
These two species were obtained by Dr. Hayden from the Judith 
River series of the Laramie Group, at the mouth of Judith River, Mon- 
tana. They are described, respectively, on pages 518 and 519 of vol. ix, 
U.S. Geol. Sur. Terr. (4to ser.), and both are figured upon plate 41 of 
the same volume. 
UNIO VETUSTUS Meek. 
UNIO BELLIPLICATUS Meek. 
Both of these species are described and figured in vol. iv, U. S. 
Geol. Sur. 40th Parallel (King), the former on p. 164, pl. 16, figs. 5 and 
5 a, b, and ¢; and the latter on p. 165, pl. 16, figs. 4 and 4 a. The 
former is also described and figured in Captain Simpson’s report of the 
Great Basin of Utah, p. 361, pl. 5, figs. 12 aand b. They are both as- 
sociated together in the Bear River series of the Laramie Group at sev- 
eral points in Bear River Valley, both above and below Evanston, 
Wyo. Dr. Peale has also brought fragments of the former from two 
or three localities still farther northward. 
UNIO GONIONOTUS* White. 
Plate 26, figs. 2 a, b, ¢, d, and e. 
Unio gonionotus White, 1676, Powell’s Rep. Geol. Uinta Mts., p. 116. 
Shell elongate subelliptical in marginal outline; flattened and thin 
when young, but becoming gibbous and even almost cylindrical when 
fully adult; dorsal margin broadly convex; base straightened in the 
adult, but broadly convex in the young shell; front regularly rounded ; 
the rounding of the posterior end somewhat irregular in consequence ot 
the presence there of the plications which end posteriorly; beaks obso- 
lete, the umbonal surface of each valve so flattened that they form an 
acute angle at the dorsum of young shells, but the angle increases in 
‘degree with age so that it is very obtuse in the adult shell. Surface of 
the anterior portion of the shell marked only by the ordinary lines and 
laminations of growth, but the posterior portion, comprising more than 
half the length, is marked by a few strong, more or less irregularly radi- 
ating plications, which begin faintly a little forward of the middle, and 
increase gradually in strength to the posterior and postero-dorsal mar- 
gins, the number being increased by a few bifurcations as the shell in 
creases in size. Curving upward and backward from the uppermost of 
* the longer plications just mentioned there are several smaller, shorter 
ones that end at the postero-dorsal margin. 
Length of the largest example in the collection 63, millimeters; height, 
35 millimeters. Young examples have very different proportions and 
shape, as is shown by figures 2 ¢, d, and e, on plate 26. 
This species differs conspicuously from any other fossil Unio known 
to me, although young examples of it bear some resemblance to those 
of the living species U. multiplicatus ; but adult examples have a very 
*This species is one of the collection made by Professor Powell at Upper Kanab, 
Southern Utah, and the only one of that collection which is illustrated in this article. 
