150 Annals of the Carnegie Museum. 



Agriochcerus viaximiis Douglass. 



Colodon cingulatiis Douglass. 



Mesohippiis bairdi Leidy. 



Mesohippus latideus Douglass. 



Hyracodon. 



Titauotheriiim. 



The Fort Logan Beds. 



The so-called Deep River Beds and their interesting mammalian 

 fauna are well known through the labors of Cope and Scott. There 

 is, however, much unavoidable confusion continually arising from the 

 use of one name for two distinct horizons. The name " Deep River ' ' 

 is used without the adjectives "upper" or "lower" and one does 

 not always know what is meant. Whether or not, as Scott thinks 

 probable, one is John Day (Upper Oligocene) and the other Loup 

 Fork, it is certain that they have different assemblages of fossils, and 

 that each should have a name by which it may be clearly distinguished. 

 The river in whose valley the Deep River beds occur is now universally 

 known as Smith River, and this is probably the true name ; though as 

 early as 1876 Grinnell and Dana called this stream " Deep Creek." 



However this may be, I do not think that this should invalidate the 

 name so long as the type locality is beyond doubt. The beds are in 

 the valley of what is now known as Smith River, between the town 

 of White Sulphur Springs and old Fort Logan and between the Little 

 Belt Mountains on the east and the Big Belt Mountains on the west.' 



Scott ^ first gave the name " Deep River beds" as a substitute for 

 Cope's " Ticholeptus beds." Scott says in his "Mammalia of the 

 Deep River Beds" (p. 59): " The upper beds which Grinnell and 

 Dana called Pliocene present a very different assemblage of species. 

 Cope's collection, so far as I can judge, was gathered entirely from 

 these beds and contains nothing from the lower horizon." It seems 

 to the writer, then, that the name Deep River should be applied to 

 the upper beds alone. 



For the older formation. Upper Oligocene (John Day?), I propose 

 the name Fort Logan beds, from the old military post a short distance 

 from the best outcrops. I do not know that this horizon is exactly 

 paralleled by any other. 



' Rep. of Reconnaissance from Carroll, Montana, to the Yellowstone National Park, 

 made by Capt. Ludlow in 1875 ; Washington, 1876, p. 1 15. 



2 Princeton Scientific Expedition of 1891. Prin. Col. Bull., III., p. 88. 



