PALEONTOLOGY OF THE BOULDER AREA IOI 



Heteroceras tortum. — One specimen from five miles north of Boulder. 



Ptychoceras sp. — Found at Four Mile Mesa, Table Mountain, and 

 west of Haystack Butte. The specimens at hand may include more 

 than one species, but they are not in good condition for determination. 



Pteria nebrascana. — A few specimens have been found at the brick 

 kilns near the University. 



Anchura haydeni. — A few, poorly preserved, found at the brick kilns 

 above mentioned. 



Anisomyon sp. — Found at Four Mile Mesa. 



Inoceramus barabini. — Widely distributed, quite variable, found in 

 many localities, particularly in this vicinity at Haystack Butte and 

 Table Mountain, where some puzzling forms referable to this species 

 have been found. Professor R. P. Whitfield, in his report on the fossils 

 of the Black Hills, described a new genus based upon the existence of a 

 posterior sulcus upon casts of specimens which would otherwise have 

 been considered Inoceramus. He called the new genus Endocostea. 

 Specimens of two species from the above-named localities indicate that 

 the existence of the sulcus and the corresponding internal rib of the shell 

 has neither generic nor specific significance. From an area of only a 

 few square yards specimens have been extracted with and without the 

 sulcus, but otherwise indistinguishable. Typical I. barabini have been 

 found, both sulcate and non-sulcate. The same is true of the next 

 species. The same thing has been noticed elsewhere by paleontologists. 

 Dr. Stanton writes, after examining part of this material: "The pos- 

 terior sulcus is a peculiar feature, but I cannot see that it has any taxo- 

 nomic value." Other specimens make the worthlessness of this feature 

 as a generic character still more evident. 



Inoceramus sublcevis. — The specimens referred to this species, from 

 Haystack Butte and Table Mountain, also include both sulcate and non- 

 sulcate specimens. They are somewhat more gibbous than Meek's 

 figures and description would indicate, and may possibly be distinct. 



Inoceramus sagensis. — This species is found on Left Hand Creek 

 and at the brick kilns near the University. Forms heretofore called 

 /. convexus are included under this name, as the two are now considered 

 identical. This species is abundant at Fossil Creek. 



