MOOK, STUDY OF THE MORRISON FORMATION 



129 



GASTROPODA 



Limncea ativuncula White, On the Fresh-Water Invertebrates of the 

 North American Jurassic. U. S. Geol. Surv., Bull. No. 29, p. 20, pi. 4, 

 figs. 10, 11, 1886. 



Limncea consortis White, On the Fresh-AVater Invertebrates of the 

 North American Jurassic. IT. S. Geol. Surv., Bull. No. 29, p. 20, pi. 4, 

 figs. 8, 9, 1886. 



Fig. 93. — Calcareous arkosic sandstone; the same rock as figs. 91 and 92. 



The large dark grains are partly replaced volcanic ash, and the large grain with 

 inclusions in the center of the field- is unaltered volcanic ash. About 28 X. 



Limncea f accelerata White, On the Fresh-Water Invertebrates of the 

 North American Jurassic. U. S. Geol. Surv., Bull. No. 29, p. 20, pi. 4, 

 figs. 12-15, 1886. 



Planorbis veternus Meek and Hayden, Phila. Acad. Nat. Sci., Proc. for 

 1860, p. 418, 1861. 



Vorticifex stearnsii White, On the Fresh-Water Invertebrates of the 



