352 CHARLES CLIFFORD MACKLIN 



of the undifferentiated sclerotomes and in its foraminal portion 

 from the body mass of the occipital vertebra. The exoccipitals 

 have been developed, as we have seen, principally from the 

 neural arches of the occipital scleromere, but in the region of the 

 foramen hypoglossi there has been added material from the lateral 

 masses of the undifferentiated scleromere. The supraoccipitals, 

 which ossify separately, are to be regarded as primarily connected 

 with the neural arch of the occipital vertebra, and their sepa- 

 rateness of ossification is analogous to the condition which we find 

 in the 5th lumbar vertebra. 



Regio otica 



The otic region, like the occipital, is transversely somewhat 

 ringlike in form, and its irregular sides, for the most part flat- 

 tened from within outwards, are united by their caudal edges 

 with the upper border of the occipital anlage, except where sun- 

 dry foramina occasion interruptions. The otic ring, accordingly, 

 heightens the dorsal part of the cartilaginous brain-case. In 

 it we recognize four distinct elements,, two unpaired, the otic 

 portion of the lamina basalis and the tectum synoticum, and two 

 paired, the otic capsule and the lamina parietalis. In addition 

 to the parts entering into the composition of the ring there 

 are also to be considered in the otic region the small, paired, iso- 

 lated nodules known as the cartilagines supracochleares, cranii 

 laterales and cranii . posteriores. 



When the skull is viewed from within (figs. 1 and 5) the upper 

 or otic portion of the lamina basalis is seen to unite the ventro- 

 median portions of the otic capsules. Passing laterally the eye 

 meets the large, irregular mass of cartilage known as the otic 

 capsule, which forms the ventro-lateral delimitation of the pos- 

 terior cranial fossa, as well as part of the floor of the middle 

 cranial fossa. Caudo-laterally the capsule is continuous with 

 the lamina alaris, and dorsal to this with the wider portion of 

 the squama of the occipital anlage, while cranio-dorsally the 

 commissura capsuloparietalis (figs. 3 and 5) is seen uniting the 

 larger dorsal portion of the otic capsule with the lamina parie- 



