GEOLOGICAL SURVEY OF THE TEREITORIES. 473 



20. Plwladomya Klngii, Meek.* 



21. Goniomya Moutanaensis, Meek.\ 



22. Ammonites Mere fragments. 



SPRING CANON, MONTANA. 



Lower bed. 



Names. Remarks. 



1^. Plants Fragments of the same forms seen at 



Devil's Slide, Yellowstone Eiver. 



2. Plicutulu An imi^erfect valve-impression of 



one valve seen in the matrix. 



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



Yellowstone. 



4. Pinna Same as No. 6, near Lower Canon, 



Yellowstone, being very like P. 

 opalina, Quenstedt. 



5. Mytilus Same as Ko. 9, from Lower Caiion, 



Yellowstone. 

 G. Modiola ( Vulsella) suhimhricata, 



Meek Same as No. 10, from Lower Caiion, 



Yellowstone. 



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



Yellowstone. 



8. Myacites (Pleuromya) siihcom- 



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



Yellowstone. 



Upper bed. 



9. Ostrea A small undetermined species. 



10. Camptonectes. 



11. Bliynchonella. 



NEAR FORT HALL, IDAHO. 



Lower bed. 



Names. Remarks. 



1. Pseudomonotis {JEumicrotis) 



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



Upper bed. 



2. Terebratula, 



3. Mytilus. 



* An elongate-oblong species, quite convex in unibonal region, with beaks moderately 

 prominent, incurved, and placed near tlie rounded anterior end. The posterior end is 

 more narrowly rounded and moderately gaping. The narrow radiating cost£B 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, i)eaks depressed, and placed near 

 the anterior end. Surface having wrinkles or costas 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 jjosterior dorsal slooes. 



