I 



ENDLicH.] GEOLOGY SAN LUIS DISTRICT, SECTION C. 341 



of those the preservation has been a rather inferior one. A number 

 of crinoids, brachiopods, cephalopods, &c., were found. The aspect of 

 several of the species reminds strongly of Upper Devonian types ; but in 

 determining here, the general character of things must be taken into 

 consideration rather than the identification of any one single specimen be 

 relied upon. Curiously enough, almost all the species found there are 

 such as have very nearly allied forms in the formations preceding, so 

 that discrimination becomes difficult. We have here a similar case to 

 one that Professor Meek speaks of in the Eeport of the United States 

 Geological Survey for 1872, page 432,in treating of the Carboniferous of 

 Mystic Lake and vicinity : "They belong, without exception, to genera 

 that are common both to the Carboniferous and Devonian, while a 

 smaller portion of the genera is also represented in the Silurian." " Some 

 of the Frochicti, Chonetes, and Bpirifer have rather a Devonian look, 

 while a fine s^triated Semipronites is very similar to some of the Devon- 

 ian types of that genus." " Notwithstanding the resemblance of some 

 of these fossils to Devonian forms, and the fact that scarcely any of the 

 species can be identified beyond doubt with forms peculiar to the Car- 

 boniferous, I must regard the whole as belonging to the lower part of 

 the Lower Carboniferous." " The entire absence of any strictly Devon- 

 ian and other types of corals, crinoids, lamellibranchs, &c., also favors 

 the conclusion that this formation belongs to the Carboniferous, which 

 conclusion is also supported by the specific affinities, if not even by the 

 specific identity, of some of the sjiecies of Spirifer, Froductus, &c." This 

 quotation applies admirably to our present case. We find — 



Numerous fragments of the columns of crinoids, not recognizable. 



Large numbers of a delicate rimose chcetetes-like coral, which is mostly 

 weathered beyond recognition of outer structure. 



An infundibular form of Fenestella, quite numerous. 



Athyris, in one small specimen. 



Spirifer^ with the medial lobe finely striated longitudinally ; the lat- 

 eral lobes containing numerous stronger, simple, radiating costsej vary- 

 ing considerably in size. 



Mkynchonella, which has a decidedly Devonian aspect. 



Orthis, a compressed resupinate form, with an extremely narrow 

 area ; probably a new species. 



Hemipronites, closely related to E. crenistria, resembling some De- 

 vonian types. 



Goniatites, in two very poor specimens. 



07~t}ioceras. 



Fi'oductus, in two specimens, that admit of some doubt, however ; one 

 fragment was found that seems to belong to a conoid univalve. 



Mesozoic beds. — None are found in section c. 



The Cretaceous formation is quite considerably developed near the cen- 

 tral western i)ortion of section c, following along Tomichi Creek. From 

 the south and west, the predominating trachorheites have overflowed 

 the sedimentary beds ; and while a considerable portion is covered by 

 them, erosion has broken through at several points, and thereby formed 

 bluffs from 100 to 300 feet in height, composed of sedimentary strata 

 and capped by volcanic material. All along the western side of the 

 valley bordering on Coochetopa Creek this is the case, and on one of 

 the bluffs station 35 is located. The greater part of the eastern jDortion 

 of them seems to be made up of Cretaceous Nos. 2 and 3, while the 

 western shows more of the lower sandstone strata. A section taken 

 through a cut in a narrow gulch to be east of station 35 gave the follow- 

 ing result, beginning from below : 



