140 



THE CERATOPSIA. 



Triceratops obtusus Marsh. 1898. 



Type (No. 4720, U. S. National Museum) consists of portion of skull from Laramie beds of Converse County, Wyo. 



Original description in Am. Jour. Sci., vol. 6, July, 1898, p. 92. 

 Nopcsa, F. Baron, Foldtani Kozlony, Budapest, 1901, vol. 31, p. 271. 

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

 Walcott, C. D., Science, new ser., vol. 11, 1900, p. 23 (T. oltusa). 



Professor Marsh described this species as follows: 



A second new species, which may be called Triceratops obtusus, is represented by a large skull belonging to the same genus. 

 The nasal horn core of this skull is very short and obtuse and so well preserved that it indicates the normal form and size. 

 The entire length of this horn core is only 1 inch. Its summit is 3J inches behind the premaxillary suture. The width of the 

 nasals beneath the horn core is 5\ inches. The length of the squamosal from the quadrate groove to the posterior end is about 

 36 inches and its greatest width is 19 inches. 



These two skulls (types of T. calicornis and T. obtusus) were both found by J. B. Hatcher in the Ceratops beds of Converse 

 County, Wyo. 



The type (No. 4720, U. S. National 

 Museum) of the present species consists 

 :S "^8=ll|w °^ a P a * r °^ mandibular dentaries and 



^%\fpmcL ^ - :i*S5^ga£§ltet^k the anterior portion of the nasals, a left 

 \^/4|a v""^^^^®^ maxillary, a squamosal, parts of a ptery- 



goid, and a vertebra. The specific name 

 was suggested by the character of the 

 «^-^ nasal horn core. The nasals, as shown 



^'^^Tl P Tl° n °! r sals °? *?%?! Tricerat ° vs ° biums Marsh in the accompanying figures, are ex- 



(No. 4720, U. S. National Museum). A, Side view; B, superior view; a, I J to fc> J 



anterior. One-eighth natural size. tremely broad, and the nasal horn core 



is reduced to a broad, rounded, and ru- 

 gose prominence, marked with a number of deep vascular grooves. 



The dentary is exceptionally deep and the teeth are unusually large. Below the base of 

 the coronoid process on either dentary the external surface of the bone presents a very sharp 

 ridge that extends continuously 



throughout about one - third of its ^^-isfov ' 



length. The posterior portion of the 

 alveolar region of the left dentary OTTj&iy 



bears evidence of having been affected f<t'i" 'pti; 1 ''M ^-iitasE?!^ / a p 



by disease and presents extensive ^%ll If 

 malformations. The mandibular fossa < ^^8JI|& 

 extends rather farther forward than is 

 common in other species of the Ceratop- ™f 



sia. The dentary is exceptionally mas- FlG - J 17 \- E f TV 1 ^ ri f * dentary of ty ? e 0l *««"**• ob y™ ; Mar f< 



J r j No. 4720, U. S. National Museum, cp, coronoid process; dp, face for 



sive and the teeth are very large. articulation with the predentary; mf, mandibular fossa. One-eighth natu- 



There are a number of foramina on ral s,ze ' 



the external surface of the dentary, as shown in the accompanying figure. 



Notwithstanding the scanty and fragmentary material upon which the present species is 

 based, it would seem to be a valid one, as indicated alike by the characters of the dentary, the 

 teeth, the nasal horn core, and that part of the nasals still preserved. 



The type of the present species was found in Converse County, Wyo., about 1 mile east 

 of Lance Creek and 2 miles southeast of the U-L ranch. The horizon would be about the 

 middle of the Laramie, as those deposits are represented in this region. The locality is shown 

 at + 9, PI. LI. 



Principal measurements of the type. 



Mm. 



Greatest length of dentary ... 670 



Greatest depth of dentary 228 



Length of dental series. . . — — 535 



Breadth of nasals at base of horn core 140 



Distance from top of nasal horn core to inferior surface of nasals 75 



