104 THE CHICAGO ACADEMY OF SCIENCES. 
which forms three-fourths of the total length; no umbilical fissure 
visible. Length, 1.20 inches; breadth, 0.75; spire, 0.30.” 
Tyee: Location not ascertained. 
Horizon: Contra Costa Lake bed, Merced series, Pliocene Period. 
Locatity: California... In thin stratum of Lignite on a small 
branch of San Pablo Creek, on the road going east to Lafayette, Contra 
Costa County (Cooper); top of Eureka Hill, Berkeley Hills; north 
base of Baldy Hill, Berkeley Hills, Alameda County (Hannibal). 
“Specimens found with the two next species in a bed of laminated 
lignite, discovered about 1868, along the westerly branch of San Pablo 
Creek, on the state road just south of Rocky Mound. A thin stratum 
of lignite underlies several square miles around that locality, but its 
exact age is still unsettled. On the east are deposits of marine Miocene 
fossils, on the west altered Cretaceous rocks with ‘Aucella piochu.’ 
The lignite may, therefore, be a deposit formed in a Pliocene lake. 
None of the other Tertiary fresh-water deposits yet examined in 
California contain fossils like this. The coal strata have evidently been 
uplifted to an angle unusual in Pliocene deposits, but there is nothing 
to fix the date of the volcanic outburst which is seen in Rocky Mound, 
three and a half miles distant.” Cooper also says: “The shells were 
crushed flat, but their outlines were so perfect and white in contrast 
with the black shale that I had no difficulty in making perfect tracings 
of them. The figures are of natural size.” 
The figure resembles a land shell (Bulimulus?) more than it does 
a Lymnaea; if a Lymnea, it is exceedingly difficult to place in one of 
the modern groups. It somewhat resembles the recent Galba apicina. 
Galba alamosensis (Arnold). Plate XVII, figures 9, 10. 
Lymnea alamosensis ARNoLD and ANperson, Bull. U. S. Geol. Surv., no, 
322, p. 59, pl. XXI, figs. 6, 7, 1907. 
Lymnea alamosensis ArNotp, Smith. Mis. Coll. L, p. 430, pl. 54, figs. 6, 7, 
1908; Nautilus, XXII, p. 36, 1908. 
“Adult shell averaging about 6 or 7 millimeters in altitude, broadly 
spindle-shaped, spire elevated, apex rounded. Whorls four, bulging, 
more convex posteriorly than anteriorly; outline of body whorl regu- 
larly arcuate; a faint ridge crowns the posterior margin of each whorl 
where it presses against the antecedent whorl. Suture appressed, 
slightly sinuous, distinct ; sculpture consisting of numerous microscopic 
incremental lines, which are somewhat better developed on the posterior 
portion of the whorl, and occasional faint spiral striz; a hard, glossy 
epidermis is preserved on some of the specimens. Aperture suboval, 
narrowing posteriorly; outer lip protruding anteriorly, thickened into 
_— -'. = 
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