394 CHARLES CLIFFORD MACKLIN 



median edge of the orbital plate of the frontal bone (fig. 2). 

 The dorso-lateral process marks the lateral extremity of the ala, 

 and also represents the ventral rudiment of the primitive taenia 

 marginalis of this region, which in the lower forms stretches 

 over the foramen sphenoparietale to make a connection with 

 the parietal plate, as has been already noted. 



The ala temporalis (fig. 10) is the smaller of the paired lateral 

 appendages of the median portion of the sphenoidal anlage. 

 It lies lateral to the Balkenplatte, and, for the most part, in front 

 of and below the level of the floor of the sella turcica (fig. 3). 

 As H. Fuchs remarks one must distinguish in the temporal wing 

 of mammals two portions; a medial, sloping steeply downward 

 and outward, and a lateral, ascending part. The medial por- 

 tion, or processus alaris, is a short, straight, rodlike mass of 

 cartilage, directly continuous with the outer edge of the Balken- 

 platte, from which, as we have seen, it projects downward, 

 outward and slightly backward. Its dorsal surface comes into 

 close contact with the cranio-ventral pole of the pars cochlearis, 

 but is not connected therewith by a cartilaginous bridge (com- 

 missura alicochlearis) , as is the case in the Jacoby model, and 

 in the models of several of the lower mammals. What I regard 

 as a remnant of this bridge is, however, to be found in the supra- 

 cochlear cartilage, which has already been described. Levi 

 was unable to find any trace of this commissure in his specimens. 



It may be noted in passing that Jacoby states that this bridge 

 extends from the lateral edge of the sella turcica to the anterior 

 edge of the ear capsule, but he has evidently included in the 

 median portion of this the structure which other authors refer 

 to as the processus alaris. Jacoby states that the ala temporalis 

 springs outward from this bridge; perhaps a better way of stating 

 it would be to say that the ala temporalis, through the pro- 

 cessus alaris, springs from the edge of the floor of the hypophy- 

 seal fossa, and that the bridge, or commissura alicochleaiis, 

 connects the ala with the anterior surface of the pars cochlearis 

 of the otic capsule. By the disappearance of the commissura 

 alicochlearis the carotid foramen is left open laterally. It is 

 quite small, being delimited ventrally by a small notch between 



