576 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



This form, though considerably smaller, is closely similar to the speci- 

 men identified by Keyes as Capulus paralius Winchell, and figured on PI. 

 LIII, fig. If?, of the work cited. 



The largest of these forms is about 9 mm. in height, with a maxi- 

 mum basal measurement of 12.5 mm. 



Formation and locality : Madison limestone, east side of Gallatin River, 

 west of Electric Peak; south slope of Quadrant Mountain, Gallatin Range; 



A. C. Gill. 



Form E. 



PI. LXVI, figs, 11a, lib, lie, lid. 



Shell rather small, though larger compared with the other forms in 

 this collection. Very rapidly expanding. Laterally compressed, being 

 flatter on the sinistral side, away from which the small coil is turned. 

 Dextral side more inflated; dorsum sharp, almost carinate. Shell marked 

 by concentric growth-lines, sinuous, following the shape of the peritreme. 

 Peritreme oval in outline. 



This should be compared with P. nebrascense Meek, 1 and more espe- 

 cially with Capahis paralius Winchell, as figured by Keyes (loc. cit, PI. 

 LIII, figs, lb, Ic), which is perhaps not identical with Winchell's type, 

 shown by fig. la of the same plate. 



Formation and locality: Madison limestone, east side of Gallatin River, 

 west of Electric Peak. 



CRUSTACEA. 



PROETUS Steininger, 1830. 



Proetus peroccidens Hall and Whitfield. 



PI. LXXI, tigs. Ua, Ub. • 



Proetus peroccidens Hall ami Whitfield, 1877 : King's U. S. Geol. Expl. 40th Par., Vol. 

 IV, p. 262, PI. IV, figs. 28-32. 



This species is represented in the Yellowstone National Park collec- 

 tions bv three cephalic shields (without the free cheeks), which are in exact 

 agreement with the description and figures of P. peroccidens. Each of the 

 three heads was found at a separate locality, but one of them occurs on the 



1 White, 1877: Wheeler's V. S. Geogr. Surv. W. 100th Merid., Vol. IV, p. 159, PI. XII, figs. oa-5d. 



