GEOLOGICAL SURVEY OF THE TERRITORIES. 473 



20. Pholadomya Kinfjli, Meek.* 



2 1 . Goniomya Mojitanaensis, Meek, t 



22. Ammonites Mere fragments. 



SPRING CANON, MONTANA. 



. Lower bed. 



Names. Remarks. 



!fc. Phints Fragmeuts of tlie same forms seen at 



Devil's Slide, Yellowstone River. 



2. Plicatula An imperfect valveiuipressiou of 



one valve seen in the matrix. 



3. Camptonectes Same as No. 4, near Lower Canon, 



Yellowstone. 



4. Pinna Same as No. (>, near Lower Canon, 



Yellowstone, being very like P. 

 opalina, (|>uensteclt. 



5. Mytilus Same as No. 9, from Lower Caiion, 



Yellowstone. 

 G. Modiola ( Vulsella) suMm hrica ia , 



Meek Same as No. 10, from Lower Canon, 



Yellowstone. 



7. Trigonia Americana, Meek Same as No. 11, from Lower Canon, 



Yellowstone. 



8. Mjjacites {Pleuromya) subcom- 



pressa, Meek Same as No. 19, from Lower Canon, 



Yellowstone. 



TJpxjer bed. 



9. Ostrea A small undetermined species. 



10. Camptonectes. 



11. lihynchonella. 



NEAR FORT HALL, IDAHO. 



Loicer bed. 



Names. Remarks. 



1. Pseudomonotls {Eumicrotis) 



curta, Hall, (sp.) Very small and in great numbers. 



Upper bed. 



2. Terebratula. 



3. Mytilus. 



* An elongate-obloug species, quite convex iu umbonal region, with beaks moderately 

 prominent, incurved, anil placed near the rounded anterior end. The posterior end is 

 more narro^vly rounded and moderately gaping. The narrow radiating costje are 

 ■wanting on the ends and posterior dorsal region ; the anterior ones (which descend 

 vertically from the beaks) are most widely separated, while those farther back are 

 more closely arranged and more oblique. 



t Elongate-oblong, moderately convex, anterior margin regularly rounded, posterior 

 truncated, dorsal and ventral margins nearly parallel, Ijeaks depressed, and placed near 

 the anterior end. Surface having wrinkles or costa) starting from before the beaks 

 and passing obliquely backward and near half way to the'base, where they die out, or 

 become very obscure, and curve horizontally backward to meet others passing down 

 the posterior dorsal sloues. 



