106 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



escape of the fourth nerve, as shown at the numeral 4- in the figures 

 of Plates 1 and 2. 



Andrews describes three closely placed foramina as being the 

 fenestra ovalis, the exit of the glossopharyngeal nerve, and that of the 

 jugular vein. One of these is certainly the fenestra ovalis, another 

 ma}' be the fenestra rotunda. The glossopharyngeal nerve and jugu- 

 lar vein may have passed out in company with the pheumogastric 

 nerve. Andrews's statement regarding the forking of the passage 

 by which the pneumogastric nerve leaves the brain cavity agrees wdth 

 what is found in Trkeratops. 



As regards the cast of the brain cavity, the figure of which is fur- 

 nished by Andrews, it seems to the writer that what is indicated as 

 the root of the eighth nerve is realh' that of the seventh, while that 

 indicated as the root of the ninth is in fact the root of the eighth. 

 From what one sees in Triceratop,s one would expect to find the root 

 of the ninth between the one just referred to and that of the tenth. 



THE P.KAIX-CASE OF :\IE(4AL()SAURrS. 



Von Huene " has written an interesting account of the brain-case 

 of Megalosavrus. This brain-case is short and high. That part of 

 the lateral wall farthest in front is regarded by V. Huene as the 

 alisphenoid. A notch at its lower end he rightly interprets as the 

 point of exit of the optic nerve. To the present writer it appears 

 that the region in front and above this notch is the orbitosphenoid. 

 That portion of the wall that lies in front of the foramen ovale, 

 rising to the parietal, must be interpreted as the alisphenoid. 



V. Huene records the presence of a " meatus auditorius externus." 

 Now, this meatus is a part of the external ear, and as this reptile 

 probably did not possess such an organ, the foramen in question must 

 have some other function. To the present Avriter it looks as if this 

 foramen might be the outlet of the depression nuirkedZ in V. Huene's 

 fig. 1. This may be the summit of an excavation that contained 

 such a process of the brain as has been described on page 103 as 

 occurring in Triceratofs. 



What V. Huene calls the jugular foramen is almost certainly the 

 inner and outer passages into the internal ear. On the inside of the 

 brain-case this foramen admitted the auditory nerve; on the outside 

 it was closed by the base of the stapes. The jugular vein doubtless 

 escaped in company with the ninth and tenth nerves. V. Huene fig- 

 ures a foramen lying some distance above the one just mentioned and 

 regards it as admitting to the inner ear the branches of the auditory 

 nerve. The structures of the inner ear must lie lower down in the 

 wall of the brain-case. Excavation of the bone lower down would 

 certainly expose the semicircular canals. It is probable that the 



° Neues Jahrb. Min., etc., 1900, I, p. 1, pi. i, text figs. 1-i. 



