HALLOPUS, BAPTANODON, ATLANTOSAURUS BEDS 339 



cliff. Its precise horizon in the cliff was never ascertained, though 

 the block of red sandstone in which the fossil was inclosed left no 

 doubt as to its derivation. This peculiar character of the matrix, 

 so different from anything found in the Atlantosaurus beds, has been 

 mentioned by Marsh, though he never gave definite information as 

 to the location of the discovery. 



Of the other specimen, that upon which was based the genus 

 Nanosaurus originally, I have no clear recollection, though I have 

 no doubt it was from the same spot and horizon as the type of Hallo pus. 

 The fact that only one-half of the split slab was obtained, as men- 

 tioned by Marsh, indicates that the specimen was not discovered 

 in situ. At the time of my first visit to Canon City, in September 

 or early October of 1877, I searched diligently in the adjacent red 

 sandstones for the Hallopus horizon, but without success. 



In July of the past year Mr. W. H. Reed, of the University of 

 Wyoming, informed me that he had, some years previously, dis- 

 covered vertebrate fossils in the red sandstones of the Red Mountain 

 region, south of Laramie City, Wyo., and very kindly took me to 

 the place of his discovery. We found there numerous fragments 

 of bones, scattered along a thin stratum, near the top of the red beds. 

 The marine Jurassic is here wanting, as at Canon City, the sandstone 

 of the Morrison or Atlantosaurus beds overlying the red beds without 

 marked unconformity. The lower members of these beds consist 

 of a grayish or yellowish sandstone, and are unfossiliferous, the first 

 vertebrate fossils occurring seventy-five feet or more above the red- 

 beds horizon. Because of an apparent absence of distinctive Triassic 

 fossils among those secured in the short time at our disposal, I was 

 somewhat inclined at the time to refer this horizon to the Lower 

 Jurassic, or possibly as a fresh-water equivalent of the Baptanodon 

 beds; the more so from the fact that the crocodile remains obtained 

 seemed to approach the mesosuchian type. 



At my request, however, Mr. Reed spent some time later in a 

 further examination of the deposits, the results of which he has 

 recently sent me. Among the material which he obtained there are 

 very characteristic labyrinthodont plates and vertebrae, proving 

 conclusively the Triassic age of the deposits. Furthermore, the 

 occurrence of the bones in the red sandstone stratigraphically quite 



