NO. 1660. SKULL OF TRICERATOPS—HAY. 107 



opening referred to corresponds to what the present Avriter has inter- 

 preted as the foramen for the fourth nerve. In V. Huene's fig. 3 

 there is represented an opening, marked T?, and thought by him to be 

 the outlet for the nerve mentioned. It appears possible that this is 

 only the anterior end of a canal that begins at the foramen assigned by 

 V. Huene to the eighth nerve. 



The Eustachian canal is mentioned by V. Ilueno as probably pene- 

 trating the vestibule (Vorraum) of the inner ear. This can not be 

 true. The Eustachian canal opens into the middle ear, that por- 

 tion l.ying outside of the fenestra ovalis and containing the stapedial 

 rod. 



Of the three foramina behind the foramen lacerum posterius the 

 one marked by X//' probably gave exit to the hypoglossal nerve; the 

 ones marked Xll" and cdv probably transmitted veins. It is not 

 probable that the internal carotid arter}- found its way into the brain 

 cavit}^ at a point so far in the rear. It certainly entered at the pitui- 

 tary fossa. 



DESCRIPTION OF PLATES. 



Plate 1. 



External view of the rear of tlio skull of two si)ecies of Triceratops. 



Fig. 1. Triceratops srrratiis. X I 

 2. Triceratops sulcatus. X g. 



nls, alisplienoiil, on the crest of the alisi)henoidal buttress to the post- 

 (iccipital; has, basisphenoidal process, brol^en a\Y!iy in fig. 1; hoc. p, basi- 

 (K'cipital process, complete in fig. 1, mostly missing in fig. 2; car, fonunen for 

 cai-otid artery, not seen in fig. 2; fen, fenestra ovalis; oc, occipital condyle, 

 pjirtly broken away in fig. 1, in fig. 2 the suture between the basioccipital and 

 the exoccipital is seen below oc; op. f, foramen supposed to be for ophthalmic 

 iirtery; orhs, orbitosphenoid ; par. p, paroccipital process, broken away in both 

 specimens; pre, presphenoid, small and not lettered in fig. 2; r, opening for 

 supposed vein; 1, 2, 3, '/, foramina for cephalic nerves of corresponding num- 

 bers; .5, external opening for ophthalmic branch of the Hth nerve; 5''", foramen 

 for exit of second and third branches of 5th nerve; 6', 7, 10, J2, foramina for 

 exit of corresponding cephalic nerves. 



Plate 2. 



Longitudinal section of the rear of the skull of two species of Triceratops, 

 showing the brain cavity; 



Fig. 1. Triceratops scrratiis. X §. 

 2. Triceratops sulcatus. X g. 



a. c. f. anterior condyloid foramen; als, alisphenoid; has, basisphenoid, 

 partly broken away in fig 1 ; hoc, basioccipital ; hoc. p, basioccipital proc- 

 ess; car, foramen for left carotid artery entering pituitary fossa, not seen in 

 fig. 2; car. g, groove for right carotid artery; ceh. f. foramen? at extremity of a 

 cerebellar process; oc, occipital condyle; op. f, foramen for exit of left ophthal- 

 mic artery from pituitary fossa; orhs, orbitosphenoid; pa, parietal; pit. f. 

 pituitary fossa; pre, presphenoid, not lettered in fig. 2; itro, ])rootic; sin, base 



