MONOCLONIUS DAWSONI. 



89 



The treatment of this material by the above-mentioned authors forms part 2 of volume 3 

 (quarto) of Contributions to Canadian Paleontology, published by the Geological Survey of 

 Canada and entitled "On Vertebrata of the Mid-Cretaceous of the Northwest Territory." 

 This memoir, consisting of 81 pages of descriptive matter, with 21 plates and numerous text 

 figures, is divided into two parts. The first of these, entitled "Distinctive Characters of the 

 Mid-Cretaceous Fauna," pages 7-21, is by Professor Osborn, and is devoted largely to a discussion 

 of the relations of the vertebrate fauna of the supposed Belly River beds to those of the Judith 

 River beds of Montana and the Laramie of Converse County and central southern Wyoming, 

 and of the Denver beds in Colorado. The second part of this memoir, "New Genera and 

 Species from the Belly River Series (Mid-Cretaceous)," is by Mr. Lambe, and is for the most 

 part purely descriptive. Three new species of Ceratopsidse are recognized and described as 

 pertaining to the genus Monoclonius. These are Monoclonius dawsoni, canadensis, and belli. 

 A new genus and species, Stegoceras validus, is also described, and erroneously referred to the 

 Ceratopsidse. The species described by Lambe will now be considered. 



Monoclonius dawsoni Lambe. 1902. 



Type (Nos. 1173 and 971, a Geol. Surv. Canada) consists of parts of two skulls from Red Deer River, Canada. 



Original description in Contr. Canadian Pal., vol. 3 (quarto), pt. 2, 1902, pp. 57-63. 

 Lambe, L. M., Contr. Canadian Pal., vol. 3 (quarto), pt. 2, 1902, pp. 68, 75, 76, 81. 

 Osborn, H. F., Contr. Canadian Pal., vol. 3 (quarto) , pt. 2, 1902, pp. 14, 20. 



The type of the present species was collected by Mr. Lambe in 1901, in the Judith River 

 beds on Red Deer River be- 

 tween Berry Creek and Dead 

 Lodge Canyon, Alberta, no more 

 exact locality or horizon being 

 given by that author. b Mr. 

 Lambe' s description is as fol- 

 lows: 



The remains of an apparently unde- 

 scribed species of this genus, consisting of 

 the skull of one individual and the pos- 

 terior crest of another, are of especial 

 interest. The skull when found lay on its 

 right side, and although very much 

 crushed, certain parts of it supply defi- 

 nite information as to its structure and 

 size. The two orbits, the right maxilla, 

 a quadrate, and the occipital condyle, 

 were conspicuous and apparently in place, 

 with a large posterior crest extending to the rear 



I foot 



Fig. 92. — Head of Monoclonius dawsoni, from a sketch in the field. One-sixteenth natural 

 size, p, Parietal; or, orbit: oc, occipital condyle; q, quadrate; m, maxilla (inner side 

 showing a row of foramina); Ji, nasal horn core; s, squamosal. After Lambe. 



Somewhat in advance of the orbits a horn core, of large size and appar- 

 ently symmetrical form, occupied a position suggestive of a nasal origin, the nasal bones and the frontals being probably 

 represented by the fragments filling the space between the orbit and the horn core (see fig. 14 [fig. 92], from a measured 

 drawing made before the parts of the skull were removed). 



The large posterior crest forms the back part of the skull above. Its exact shape is fortunately supplied by the admir- 

 ably preserved specimen shown in outline, from beneath, in fig. 15 [fig. 93]. The surface of the bone, above the orbit and 

 from there inward for a short distance toward the median line of the skull, is moderately smooth and shows no trace of a 

 horn core. 



With the separate posterior crest was found a horn core, similar in shape to, although not as well preserved as, the one 

 belonging to the skull. 



The posterior crest is composed of the parietals and squamosals coalesced. The former are represented by a flat, thin, 

 smooth median portion that expands laterally both in front and behind. Anteriorly it is deeply concave below and broadly 

 convex above, but posteriorly it thickens gradually, and dividing to either side is continued forward as the squamosals in 

 a broad curve to meet the anterior expansion. On either side of the median element is included a large supratemporal 

 vacuity or fontanelle. 



a This specimen, No. 971, here figured (fig. 93) and described has since been made the type of a new genus and species. See footnote, p. 

 93.— R. S. L. 

 i See p. 179. 



