THE CHICAGO ACADEMY OF SCIENCES. 



which forms three-fourths of the total length; no umbilical fissure 

 \isible. Length, 1.20 inches; breadth, 0.75; spire, 0.30." 



TYPE : Location not ascertained. 



HORIZON : Contra Costa Lake bed, Merced series, Pliocene Period. 



LOCALITY: 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 piochii' 

 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 Lymncea; if a Lymncea, 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. 



Lymncea alamosensis ARNOLD and ANDERSON, Bull. U. S. Geol. Surv., no. 

 322, p. 59, pi. XXI, figs. 6, 7, 1907. 



Lymnaa alamosensis ARNOLD, Smith. Mis. Coll., L, p. 430, pi. 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 striae; a hard, glossy 

 epidermis is preserved on some of the specimens. Aperture suboval, 

 narrowing posteriorly; outer lip protruding anteriorly, thickened into 



