362 ^ ROBERT J. TERRY 



and pars canalicularis is likewise seen in cat, but the relation is 

 apparently not the primary one. The primary lateral termina- 

 tion of the suprafacial commissure in the cat is not in the otic 

 capsule, but in the commissura orbito-parietalis, where the 

 latter meets the prominentia ampuUaris superior. Continuity 

 with the orbito-parietal commissure (a part of the lateral cranial 

 wall) and, at the same time, partial separation from the otic 

 capsule, is to be regarded as evidence pointing toward the 

 parietal nature of the suprafacial commissure. While I find no 

 reference to a relation between the suprafacial commissure and 

 cranial side wall in descriptions of mammalian chondrocrania, 

 the constant proximity of these parts strongly suggests that the 

 continuity seen in cat may obtain in other mammals. De 

 Burlet's figures of the Balaenoptera chondrocranium are of 

 great interest in this connection. Further support of the view 

 of the parietal nature of the suprafacial commissure is offered 

 by the relation of this structure to the exit of the trigeminus. 

 As stated in the description of the orbito-temporal region, the 

 roots of this nerve and the semilunar ganglion lie between the 

 suprafacial commissure and a thickened band of the transverse 

 septum in which is developed an accessory cartilaginous rod 

 resting upon the dorso-medial surface of the ganglion. A simi- 

 lar structure was observed in the rabbit by Voit who inter- 

 preted the 'Restknorpel b' as possibly representing the pila 

 prootica of Lacerta, a structure of the primary cranial wall. In 

 Lacerta the trigeminus makes its exit by way of the prootic 

 fenestra whose boundaries are the prootic pillar and prefacial 

 coixanissure. In the cat the fifth nerve leaves the cranial cavity 

 between the accessory cartilaginous rod and the suprafacial 

 commissure. Continuity of the anterior part of the otic cap- 

 sule with a portion of the lateral wall of the cranium in the 

 cat should make us hesitate in assigning entirely otic boundaries 

 for the facial canal. The evidence so far indicates possibly that 

 the foramen faciale in the cat stands in the boundary zone 

 between the pars cochlearis of the otic capsule and the cranial 

 wall, represented by the suprafacial commissure. Such a rela- 

 tion is in harmony with that which obtains in reptiles, to the 



