220 BULLETIISr UNITED STATES GEOLOGICAL SUEVEY. [VolY. 



of P. grctyvillensis, as given by ]srorwpocl and Pratten, to warrant their 

 separation under a new specific name. The principal differences pre- 

 sented by these examples are the greater j)rominence of the band-bear- 

 ing carina, the more distinct furrow separating it from the proximal 

 portion of the volution, and the greater prominence of the revolving 

 lines which cover the surface. 



CRETACEOUS FORMS. 



Among some fossUs sent for examination to the office of the Survey by 

 Mr. Arthur Lakes, who collected them from the Cretaceous strata on 

 Fossil Creek, sixteen miles west of Greeley and gix miles south of Fort 

 Collins, Colorado, are specimens of two corals which have to a remark- 

 able degree a Paleozoic facies. Mr. Lakes's known familiarity with the 

 geology of that region would of itself incline me to refrain from ques- 

 tioning the correctness of his reference of these fossils to Cretaceous 

 strata, notwithstanding their Paleozoic facies ; but fortunately he has 

 made such questioning imi30ssible by sending pieces of rock in which 

 both the corals and well-known species of Cretaceous shells were im- 

 bedded together. Besides this, I have myself visited that locality, and 

 recognize the strata there as belonging to the lower portion of the Pox 

 Hills Group of the Cretaceous series, as that group is developed in Colo- 

 rado, and doubtless equivalen j with a portion of the Port Pierre Group, 

 or Cretaceous No. 4 of the Upper Missouri Eiver region. 



Corals are exceedingly rare in any of the Cretaceous rocks of Western 

 North America, and therefore the discovery of any coralline form is of 

 more than ordinary interest j but the interest concerning these two forms 

 is greatly increased by their apparent Paleozoic affinities. Being im- 

 bedded in sandstone, the condition of their preservation is not such as 

 to give entirely satisfactory results from their study. I have therefore 

 referred them provisionally to Paleozoic genera, because in their visible 

 characteristics they correspond more nearly with those" genera than with 

 any others known to jne. 



Professor H. AUeyne Mcholson, of the University of St. Andrews, 

 Scotland, whose labors in the fossil Actinozoa and Polyzoa are well 

 known, has kindly examined specimens of both these forms at my solici- 

 tation, and to him I am indebted for valuable notes concerning them. 



ACTINOZOA. 



Genus Ch^etetes Fischer. 



Chaetetes? ? dimissus (sp. nov.)- 



Corallum ramose, dichotomously branching at irregular intervals; 

 branches cylindrical or subcylindrical, solid, the successive branches 

 diminishing in size. Corallites rather small, closely compacted, diver- 

 ging from the center, with a slight upward curve, to tlie surface, and 



