1 6 ALLIS. [VOL. I. 



trochlearis, and abducens nerves, and the ophthalmic division of 

 the trigeminus, the probable homologue of the profundus (No. 

 2, p. ooo) issue through the sphenoidal fissure, between the 

 orbitosphenoid and alisphenoid; the superior maxillary division 

 of the trigeminus issues through the foramen rotundum, said 

 by Thane to be cut off from the sphenoidal fissure, but from 

 Jacoby's descriptions (No. 16, p. 67), lying apparently posterior 

 to the alisphenoid; and the inferior maxillary division of the 

 trigeminus issues through the foramen ovale, which is cut off 

 from the foramen lacerum, which lies between the alisphenoid 

 and periotic. 



The sphenoidal fissure of man was shown in my earlier work 

 (No. 2, p. ooo) to agree strikingly in position and function with 

 the tall orbital opening of the eye-muscle canal of Amia, and to 

 be apparently the homologue of that opening. It is accordingly 

 also, in whole or in part, the apparent homologue of one-half of 

 the orbital fontanelle of teleosts. 



In mammals, each half of the orbital fontanelle of fishes seems 

 to be represented in a large opening, closed by membrane, which 

 lies, according to Sternberg (No. 3, p. 147), between the two 

 sphenoid bones and transmits the orbital nerves and vessels. 

 The canalis craniopharyngeus lateralis of Sternberg, found in 

 man and many mammals, is then the last remnant of the ventral 

 part only of the tall orbital opening of Amia, and not a last 

 remnant of the entire opening, as Bardeleben's statement of 

 Sternberg' s conclusions seems to indicate. 



The petrosal bone, which lies in man posterior to the sphe- 

 noidal region of the skull, but which in fishes may, as shown 

 above, invade that region to a considerable extent, and the facial 

 nerve, which should lie morphologically in front of the petrosal, 

 if that bone lies between successive segmental nerves, as its 

 position in Amia seems to indicate, must now be considered. 



The facial nerve in man leaves the primordial cranium, 

 according to Vrolik, by the hiatus Fallopii and not by the 

 stylomastoid foramen (No. 32, p. 308). This statement is based 

 on the fact that in human embryos of from 12 cm. to 15 cm. in 

 length, the nerve lies, after issuing from the hiatus, in a groove 

 in the cartilage of the under surface of the skull (No. 32, 



