PRIMORDIAL CRANIUM OF THE CAT 383 



of the cave, comes into the primary cranial ca^dty. Recently, De 

 Burlet ('13) has brought forward evidence of the carotid in Pho- 

 caena traversing the trabecula or its equivalent. In the por- 

 poise the carotid passes directly into the primary cranial cavity. 

 As we have seen, the luniting membrane in the cat is fixed to the 

 basis cranii, neither to one or the other side of the carotid fora- 

 men, but broadly over the region where the vessel enters. It is 

 attached both to the alicochlear commissure and to the lateral 

 margin of the sella turcica. The former does not, in the cat, 

 enter into the floor of the ca\^um epiptericum, nor does the ca- 

 rotid artery pass directly into the primary cranial cavity. The 

 vessel first traverses that part of the membrana Umitans which 

 is fixed to the cranial floor, before passing into the original cavity 

 of the skull. As to the homology of the commissura alicochlearis, 

 it is evident that if the processus alaris is not included as a part 

 of it, the diflficulty of comparing the commissure with the tra- 

 becula cranii is much increased ; if the alar process be recognized 

 as the continuation of the ahcochlear conmaissure forward, in 

 continuity \\ith the median basal cartilage of the orbito-temporal 

 region, the comparison is far less difficult. Reviewing the con- 

 clusions stated above, we may note, first, that the name commis- 

 sura alicochlearis is a misnomer, since it does not express the true 

 relation of the commissura, but implies a connection \\ith. the 

 ala temporalis which does not exist in the mammals so far studied. 

 Secondly the studies of Noordenbos on the mole and my own on the 

 cat show that the so-called processus alaris may be simple or com- 

 pound in different animals, but that it is primarily a part of the 

 commissura ahcochlearis (its anterior end in fact), continuing into 

 the median basal cartilage; relation of the processus alaris to 

 the ala temporalis is secondary and obtains in those types (mole) 

 where the ala springs from the basal cartilage; its root, at first 

 separate from, later becomes fused with, the processus alaris to 

 produce the compound form of alar process. When the ala 

 temporahs is independent of the basal cartilage (cat) the former 

 has nothing to do with the processus alaris, which then is the 

 simple extension forward of the commissura ahcochlearis into 

 the sella turcica. 



