102 THE CHICAGO ACADEMY OF SCIENCES. 



MIDDLE MIOCENE LYMN.EAS. 



Lymnaea stearnsi Hannibal, Ms. Plate XYII, figure 11. 



Limncea maxima Stearns, Science, X. S., XX, p. 134. 1'j02 ; Univ. Cal. 

 Pub., Geology, V, p. 70, fig. 1, 1906. ( Xot Limncca stagnalis var maxima Col- 

 lin, Ann. Soc. Mai. Belg, VII, p. 94, 1872.) 



"Partly exposed in portions of a fine compressed sediment of 

 lacustrine origin are several casts of a very large Limncca, suggestive 

 in a general way of the circumboreal stagnalis, but so much distorted 

 as to preclude a more definite description.'' (Stearns.) 



Type: Uni. Cal., Coll. Invert., no. 10002. 



Horizon : Mascall beds, Middle Miocene Period. 



Locality : Three-quarters of a mile east of Belshaw's ranch, 

 Grant County, John Day Valley, Oregon. 



Remarks : The known specimens of stearnsi are so imperfect 

 as to preclude an accurate discussion of the relationship of the species. 

 Apparently it was a species similar to the recent stagnalis, judging by 

 the size and form of the casts, and there is good reason to believe that 

 it is a representative of the early Asiatic invasion and, hence, an an- 

 cestor of the recent Lymncca stagnalis. More material is highly de- 

 sirable, especially those showing the external character of the shell. 

 Of the known fossil Lymnjeas. stearnsi is the nearest approach to the 

 typical genus, containing the circumboreal stagnalis. 



pliocene lymn.eas. 



Polyrhytis kingii (Meek). Plate XVII, figures 1. 2. 



Limncca (Polyrhytis) kingii Meek. U. S. Geol. Surv. Terr.. IX. p. 532, 

 1876; U. S. Geol. Surv. 40th Parallel, IV, p. 192, figs. 6, 7, 1877.— White, Bull. 

 U. S. Geol. & Geog. Surv., Ill, p. 614, 1877.— Marcou, Proc. Xat. Mus., VIII, 

 p. 340, 1885. — Schuchert, Bull. U. S. Xat. Mus., 53. i, p. 356, 1905. 



Limncca kiiigi, Miller, Journ. Cin. Soc. Xat. H., IV. p. 121, 1881. — White, 

 3rd An. Rep. U. S. Geol. Surv.. p. 446, pi. 32, figs. 30-31, 1883.— Tryon, Struct, 

 and Syst. Conch., Ill, p. 101, 1884. — Baker, Science, n. s., XXVII, p. 943, 1908. 



Lymncca, sp.. King, U. S. Geol. Surv. 40th Parallel, I, p. 436, 1878. 



"'Shell: Ovate; spire short; volutions about four, convex, rap- 

 idly increasing in size, last one very large and ventricose ; suture well 

 defined; aperture large, subovate; columella apparently with a mod- 

 erately well-developed fold ; surface ornamented by regular, distinct 

 vrtical costae, that are strongly defined on the body-volution, but more 

 obscure or nearly obsolete on the spire. 



''Length, 0.73 inch; breadth, about 0.43 inch." ('Meek.) 



Type: U. S. Xat. Mus., no. 809; (Holotype). 



