184 EEPOET UNITED STATES GEOLOGICAL SURVEY. 



24. Mactra (CymhopJiora) warrenana Meek & Hay den. 



This species was found in the upper strata of the Fox Hills Group, both 

 at the mouth of the Saint Vrains and near Aaron Eaton's farm in the 

 valley of the Cache a. la Poudre ; also, at Fossil Eidge, the strata of 

 which are near the base of the group. The examples from both the lat- 

 ter and the first-named localities are referred to this species without 

 hesitation, but those of the second-named locality appear to agxee more 

 nearly with the description of M. {G.)formosa Meek & Hayden. How- 

 ever, I regard the difference between these two forms as varietal only. 

 The range of the species is through the whole of the Fox Hills Group as 

 developed in Colorado east of the Rocky Momitains, but it seems never 

 to have been found in the Fort Pierre division in the Ui>i3er Missouri 

 Kiver region. 



25. FJwladomya? 



A single fragment, evidently belonging to this genus, was found at the 

 mouth of the Saint Vrains. It is plainly different from P. sitbventricosa 

 Meek & Hayden, which has been found only in strata holding a similar 

 stratigrai)hical position at the mouth of Judith River. It is probably 

 new, but the specimen is too imperfect for characterization. 



26. Glycimeris hertlioudi White. 



This fine species has been found only at Fossil Eidge, in strata near 

 the base of the Fox Hills Group. It is figured and described in another 

 part of this volume. 



27. Fachymya f lierseyi White. 



This species is figured and described in another part of this volume. 

 It was found by myself only in the upper i)art of the Fox Hills Grouj) as 

 developed in this district, and only at the mouth of the Saint Vrains 

 and in the vallej^ of the Cache a la Poudre; but Mr. A. Lakes has 

 obtained it from a similarly high horizon in the valley of Bear Creek, 

 near Morrison, Colo. It is figured and described in another part of this 

 volume. 



28. Teredo? 



In a fragment of fossil wood obtained among the other fossils at Little 

 Thompson Creek I detected borings, e^idently of Teredo, or an allied 

 form, but they were too imperliect for specific determination. 



29. Dentalium gracile Hall & Meek. 



Our examples were found in considerable numbers in the u]ipermost 

 strata of the Fox Hills .Group at the mouth of the Saint Vrains and in 

 the valley of the Cache a la Poudre. They were found only in the form 

 of casts, which, not showing the surface characters very clearly, leave a 

 little doubt whether they may not really belong to another species, but 

 they seem to be identical with D. gracile. The type specimens were 

 obtained from the upper beds of the Fort Pierre Group in the tipper 

 Missouri River region. 



■ 30. Cyliclma scitula Meek & Hayden. 



The type-specimens of this species were obtained from the Fox Hills 

 ' Groui) on the Moreau River, a tributary of the Upper Mis'souri. It 

 , seems not to be a common species, as it has not been reported from any 

 • other locality until it was found in the district here discussed. I foimd 

 it only in the uppermost strata of the Fox Hills Grouj:), and only at the 

 anouth of the Saint Vrains and in the valley of the Cache a la Poudre. 



