TOROSAUKUS LATUS. 



151 



DESCRIPTION OF THE TYPE. 



The type of the present genus and species consists of a skull (No. 1830, Yale Museum) 

 without the lower jaw. The posterior portion of the parietals, the summits of the supraorbital 

 horn cores, the rostral, premaxillaries, and a considerable portion of the maxillaries are also 

 wanting. 



The frill or posterior portion of the skull is greatly expanded, both transversely and antero- 

 posteriorly, and was pierced by two large supratemporal fontanelles. Only the antero-external 

 border of the left one of these fontanelles is preserved in the type, so that it is not possible to 

 determine with certainty either their form or dimensions. Marsh has figured them as elliptical, 

 and his figure is reproduced here as fig. 118. 



According to Marsh the squamosals form the postero-external borders of the fontanelles, 

 though I am unable to tell, after an examination of the type, whether or not this is the case. 

 It may be that, as in the fol- 

 lowing species of this genus, 

 these fontanelles were entirely 

 inclosed by the parietals. 



In the present genus the 

 parietals form a considerably 

 greater portion of the frill 

 than in Triceratops, and the 

 squamosals are eorrespond- 

 mgty smaller, being reducedi 

 to long, narrow, blade-like 

 bones on the external mar- 

 gins of the parietals, very 

 narrow behind but broader 

 in front. The skull is ex- 

 tremely broad and massive 

 between the orbits and the 

 anterior extremities of the 

 squamosals, while in front of 

 the orbits the facial region 

 narrows rapidly and appears 

 very short and compressed 



when compared with the broad and elongate posterior crest or frill. In front the parietals pre- 

 sent two large irregular-shaped fossa?, situated one on either side, which are doubtless connected 

 by foramina with the large cavities in the postfrontals at the bases of the horn cores. Just 

 within and near the antero-internal borders of these two large fossae two foramina pierce the 

 parietals. From the external openings of these two foramina two broad, shallow grooves run 

 forward and upward on the surface of the skull, rapidly converging and terminating in two 

 foramina, separated by a thick partition of bone, which marks the median line of the 

 skull. These two foramina are doubtless homologous with the single median one usually 

 found in this region in skulls pertaining to the genus Triceratops and known as the postfrontal 

 foramen or pineal foramen of Marsh. Owing to the age of the individual, the sutures 

 in this region are so much obliterated that it is quite impossible to determine whether these 

 foramina are located in parietals or postfrontals. In the type of the following species, 

 which pertains to a younger but larger individual, they appear to have been located entirety 

 within the parietals. This being the case, it would not be technically proper to call them post- 

 frontal foramina, even though they are homologous with that element in the genus Triceratops. 



Fig. 118. — Dorsal aspect of skull of type of Torosaurus latus Marsh, No. 1830. Yale Museum. 

 One-twentieth natural size, c, Supra-temporal fossa; c'. anterior temporal foramen: 

 /', parietal fontanelle; h, supraorbital horn core; h', nasal horn core; p, parietal; s, squa- 

 mosal. After Marsh. 



a See footnote on p. 24.— R. S. L. 



