90 THE CHICAGO ACADEMY OF SCIENCES. 



fold, and showing by the side of the inner lip below, appearances of 

 a small umbilical indentation. Surface marked by fine, rather obscure 

 lines of growth, with (on some specimens) exceedingly faint traces 

 of microscopical revolving striae. 



"Length, 0.40 inch ; breadth, 0.20 inch ; apical angle convex, di- 

 vergence 40" (Meek). 



TYPE : U. S. Nat. Mus. no. 685 ; no. 23116 ; plesiotypes no. 12500. 



HORIZON : Bear River formation, 1 Cretaceous Period. 



LOCALITY : Bear River, near mouth of Sulphur Creek, Uinta 

 County, Wyoming; Mellis Station, Bear River Valley; 20 miles north 

 of Cokeville, Uinta County, southwestern Wyoming, embedded in thin 

 layers of impure limestone. 



REMARKS: "Among recent species, this may be compared with 

 L. humilis and the several forms regarded by Mr. Binney as varieties 

 of this species. It is a decidedly more slender shell, with a less ex- 

 panded aperture and less developed inner lip than Mr. Binney's figure 

 (p. 63, fig. 99, Land and Fresh- Water Shells) of an authentic specimen 

 of that species. It agrees, however, more nearly in form with some 

 of those figured by Mr. Binney as varieties of L. humilis, but still 

 differs from them all in other details" (Meek). 



As stated by Meek, this species bears a close resemblance to the 

 recent Galba humilis (Say), 2 and it undoubtedly groups with that 

 species. There seems to be some confusion regarding this species. 

 In his discussion of the Bear River formation, Dr. White remarks as 

 follows : 3 



"Ever since the first publication of this species, more or less doubt 

 has prevailed as regards its specific and generic characters, the locality 

 and formation from which it was first obtained, and the identity of 

 the type specimens. I have hitherto been somewhat disposed to regard 

 it as identical with the form which is described on a following page 

 under the name of Charydrobia stachei, and I should, therefore, have 

 rejected it from this summary of the fauna of the Bear River for- 

 mation if it were not that a considerable number of specimens have 

 lately been obtained which conform well to the original description 

 as published by Mr. Meek. The specimens believed to be those which 

 were thus originally used by him are figured on plate VI. They are 

 preserved in the collections of the United States National Museum, 



a The writer agrees with Dr. "White that the fauna of the so called Bear 

 River formation is sufficiently distinct from that of the Laramie to justify its 

 separation on this ground even though its stratigraphical relations may not 

 Justify such a procedure. 



2 The resemblance to G. humilis modicella is remarkable. 



'Bull. 128, U. S. Geol. Surv., p. 45. 



