142 NON-MARINE FOSSIL MOLLUSCA. 



PLATE 31. 



All the forms represented on this plate occur iii the fresh-water Eocene deposits of 

 Wyoming, Colorado, and Utah; and all are believed to be genetically related. They 

 have been described by different authors under six respective names, according to the 

 variation of ornamentation and form. (See remarks on page 58.) 



Figs. 1, 2, and 3 may be regarded as representing the Goniohasis simpsoni of Meek; 

 Figs. 5, 10, 12, a.nd others, 6>. tenera Hall; Figs. 14, 15, 20, and others, G. nodulifera 

 Meek; Figs. 19, 25, 28, and others, G. carteri Conrad; aud Figs. 29 and 30, G. colnminis 

 White. Fig. 31 is a copy of Meek's figure of G. arcta, which he finally regarded as 

 only a variety of his G. simpsoni. It, is however, very like a form which occurs in the 

 Laramie beds of Bear River Valley in Southwestern Wyoming. 



