610 JOHN D. KERNAN, JR. 



dorsal foraminal prominence, a protuberance on the edge of the 

 foramen magnum, just below the junction of the occipital wing 

 with the parietal plate. This thick round border has been iden- 

 tified by Bardeen ('10), as the neural arch of the occipital 

 vertebra. 



From the lateral aspect of the cranial border of the occipital 

 wing a prominent flange of cartilage protrudes which gives to 

 the occipital wing a lateral extension already mentioned as the 

 lamina alaris (figs. 2, 7, 2). The ventral tip of this structure is 

 known as the paracondyloid process (figs. 2, 6, 1). The lamina 

 as a whole has cranial and caudal surfaces, lateral and mesial 

 borders, dorsal and ventral extremities. Its relation to the oc- 

 cipital wing on the one hand, and to the otic capsule on the other 

 are very important. In the sections it is seen to consist of two 

 parts, as concerns its cartilage, a lateral and a mesial (fig. 5). The 

 mesial part is a lateral protrusion of the occipital wing (fig. 5, 5). 

 The lateral part is a bar of cartilage parallel to the mesial ridge, 

 and in close contact with it, but showing a separation of its 

 cartilage at certain levels. It is entirely independent at the 

 tip (fig. 6, 1). Then for a distance dorsal to the tip it is in close 

 contact with the mesial part, but separated from it by a layer of 

 perichondrium, (figs. 4 and 6, right side). Dorsal to this area 

 of close contact, there is for a distance a fairly wide separation, 

 then an area of complete fusion. Still more dorsally there is 

 again an area of separation (fig. 5), then complete fusion (fig. 

 7, 5), which is not again interrupted. 



The cranial surface of the lamina alaris forms the caudal 

 boundary of the jugular foramen ventrally, and of the jugular 

 recess dorsally (fig. 1, 4, 34). The caudal surface is free. The 

 mesial edge is in relation to the outer aspect of the occipital wing 

 as already described. The lateral edge is prominent ventrally, 

 becomes low more dorsally, and gradually fades into the outer 

 surface of the occipital wing. It is the inferior nuchal line of the 

 exoccipital portion of the adult bone (fig. 2, 38). 



The cranial aspect of the lateral edge of the lamina alaris (fig. 

 7, 5), is united to the otic capsule. The point where the two 

 structures first come in contact marks the lateral limit of the 



