102 THE CHICAGO ACADEMY OF SCIENCES. 



MIDDLE MIOCENE LYMN^AS. 



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



Limnaza maxima STEARNS, Science, N. S., XX, p. 154, 1902; Univ. Cal. 

 Pub., Geology, V, p. 70, fig. 1, 1906. (Not Limncea stagnalis var maxima COL- 

 UN, 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 Limncea, 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 Lymncea stagnalis. More material is highly de- 

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

 Of the known fossil Lymnseas, stearnsi is the nearest approach to the 

 typical genus, containing the circumboreal stagnalis. 



PLIOCENE LYMN^EAS. 







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



Limnaa (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. Nat. Mus., VIII, 

 p. 340, 1885. SCHUCHERT, Bull. U. S. Nat. Mus., 53, i, p. 356, 1905. 



Limn&a kingi, MILLER, Journ. Cin. Soc. Nat. 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. 



Lymncea, 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 costse, 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. Nat. Mus., no. 8097 (Holotype). 



