180 THE CERATOPSIA. 



are more readily accessible from Edgemont, S. Dak., on the Burlington and Missouri division 

 of the Chicago, Burlington and Quincy. The Ceratops beds first appear about 25 miles north 

 of Lusk — 



occupying the summit and northern slope of a yellow sandstone ridge extending in a westerly direction from Buck Creek to 

 Lance Creek and crossing the latter stream near the mouth of Little Lightning Creek, a small tributary from the west. A 

 short distance west of Lance Creek the Ceratops beds pass under other beds composed of very similar material and presumably 

 of Cretaceous a°"e. From Buck Creek the eastern border of the Ceratops beds has been traced in an almost continuous 

 exposure extending northeastward to the Cheyenne River and crossing this stream a short distance below the mouth of Lance 

 Creek. From this point it takes a more northerly direction and, skirting the western slope of the Black Hills, it has been 

 traced to the north line of Converse County and on into Weston County. * * * The Ceratops beds were originally confined 

 to the western slope of the Black Hills and of the less elevated series connecting the latter with the Rawhide Range. * * * 

 In no instance have the Ceratops beds been observed east of the Black Hills or their less elevated continuation to the southwest. 

 The Ceratops beds proper — that is, those beds containing remains of the Ceratopsida? — are known to have a surface 

 exposure in that portion of Converse County embraced within their eastern and southern border, as defined above, and a 

 line extending from that point on the latter where it passes under the overlying beds a short distance west of Lance Creek, 

 nearly due north to Weston County, i. e., the country drained by lower Lance, Lightning, Cow, Doegie, and Buck creeks, 

 and that portion of the Cheyenne River and its tributaries between the mouth of Lance Creek and the north line of Converse 

 County. 



Most of these creeks are shown on PL LI, which was originally drawn by Hatcher to accom- 

 pany the paper just cited, but was not published until later. ° 



The Ceratops beds are made up of alternating sandstones, shales, and lignites, with occasional local deposits of limestones 

 and marls. The different strata of the series are not always continuous, a stratum of sandstone giving place to one of shales 

 and vice versa. This is especially true of the upper two-thirds of the beds. The lack of continuity has rendered it well nigh 

 impossible to establish any definite horizons in the upper members of the series. All the deposits of the Ceratops beds of this 

 region bear evidence of having been laid down in fresh waters. Among the invertebrate fossils found in them, only fresh- 

 water forms are known. * * * 



The sandstones largely predominate in the lower members of the beds. They are always fine grained, massive to well 

 stratified, and nearly white to yellowish brown in color. They are occasionally compact and hard, but for the most part quite 

 soft and friable. * * * Almost everywhere in the sandstones are numerous concretions of varying size and shape. Some 

 are almost perfect spheres and vary from the size of a marble to 18 to 20 feet in diameter. Others are from a few inches 

 to several feet in transverse diameter and sometimes several hundred feet in length, a cross section forming a nearly perfect 

 circle. Others still are very irregular in form. These concretions usually show no concentric structure, and while they some- 

 times inclose foreign objects, as a Triceratops skull or a single bone as a nucleus, they are for the most part simply centers 

 of solidification and not true concretions. This is frequently shown by the cross bedding in them, so often seen in the sand- 

 stones themselves. * * * 



The lignites occur in thin seams, never more than a few inches thick, of only limited extent, and with many impurities. 

 At no place in the Ceratops beds of this region have workable coal beds been found. 



The exact localities of the type specimens from the Converse County beds are as follows: 



Triceratops Jiorridus at the point marked + 1, PI. LI, on the south side of a canyon entering 

 Buck Creek from the west and about 5 feet from the bottom of the canyon, contained in a 

 concretion formerly embedded in a light-yellow, soft, heavily bedded sandstone. 



Stratigraphically T. Jiorridus came "from midway between the Fox Hills and Fort Union" 

 of Converse County. Hatcher estimates the stratigraphical range from the locality of the 

 type of Ceratops montanus to that of the present species as 3,500 feet, allowing 2,000 feet for 

 the Bearpaw shales and true Fox Hills sandstones arid 1,500 for the Laramie below the 

 skull level. (See p. 119.) 



The type of Triceratops (Sterrholopbus) flabellatus was found at the point marked +2 in PL 

 LI, where "it lay in a bed of arenaceous shale, at the summit and the extreme western point 

 of a high and rocky ridge about half a mile in length, running westward from the main divide 

 between Buck Creek and Lance Creek." 



Stratigraphically it lay above the position of any other type, with the possible exceptions 

 of T. sulcatus and T. brevicornus. 



Triceratops prorsus, type, lay at the locality marked +3 in PL LI. It was situated on Dry 

 Creek, which empties into Lance Creek from the west, about 3 miles above the mouth. It 

 lay on the north side, about 100 yards above the location of the type of T. serratus, in a hard 



" Am. Naturalist, Feb., 1896, vol. 33, PI. III. 



