The Cbondrocranium of an Embryo Pig. 195 



a small thick plate, triangular in shaj^e, with the broadest side facing 

 toward the rear and the opposite angle directed antero-ventrally ; to 

 its median corner the processus alaris is attached. Its antero-dorsal 

 surface is hollowed out for the reception of the ganglion semilunare 

 (Gasseri). Anteriorly the ala is bounded by the fissura orbitalis 

 superior and posteriorly by the foramen lacerum. Through the 

 former there pass the oculomotor, trochlear and abducens nerves, 

 as well as the first two branches of the trigeminal. Through the 

 foramen lacerum the third branch of the trigeminal nerve and the 

 internal carotid artery pass. ISTo foramina perforate either the 

 processus alaris or the ascending part of the ala temporalis, nor are 

 there any notches in their borders for the passage of blood-vessels 

 or nerves. Contrasting the ala temporalis of Sus with that of some 

 other mammals, many differences are noted. In the first place, in 

 Talpa the processus alaris seems more like a broadened-out portion 

 of the basal cartilage than like a rod, as in Homo, Echidna and 

 Sus, in which forms it is well differentiated from the basal cartilage. 

 In Sus the ala temporalis is small, a character which may be due, in 

 part, to the young stage from which my reconstruction was made. 

 The absence of foramina or fissures in its border has been noted 

 above. In Talpa there is a broad connection with the otic capsule 

 through the tsenia alicochlearis, while in Sus there is no indication 

 of such a rod. 



In earlier stages of some mammals (Homo, Felis, Canis, and 

 Ursus cf. Winzca, 1896) the ascending part of the ala temporalis is 

 formed first as a separate piece of cartilage and then later unites 

 with the processus alaris. Ko indication of such a separate forma- 

 tion has yet been described in Sus and yet I venture to predict that 

 such a condition will be found, since in my series of sections the 

 middle of each processus alaris is constituted of less dense cartilage 

 than the alse or the median rod (Fig. 7, pr. al.), indicating that it may 

 have been formed subsequently to these. 



Gaupp holds (1902) that the cavum cranii in the mammals is 

 not the equivalent of that in the reptiles, but that it has been in- 

 creased by the addition on each side of an accessory cavity (Nehen- 

 raum), the cavum epiptericum. This additional cavity in the mam- 



