706 B. W. KUNKEL 



terior direction, as is also indicated bj- the relation of the nervus 

 glossopharj'ngeus to the otic capsule. This change in relations 

 may be imagined to have taken place by supposing that the 

 posterior extension of the floor of the cochlea has occurred prin- 

 cipally in front of the fenestra cochleae and has been more rapid 

 on the antero-ventral aspect of the sac than on the postero-dorsal. 

 In this event it is apparent that a foramen, for example, which 

 originally lay in the floor of the capsule will be rotated to occupy 

 the posterior wall. In the same way also, should the growth in 

 a posterior direction be more rapid laterally than medially where 

 the proximity to the basal plate would retard the extension, 

 the external aperture of the recess would come to be somewhat 

 posterior to the internal aperture. 



CAPSULA OTICA 



In general form the otic capsule may be compared to a trian- 

 gular prism with one long edge situated ventrally and with the 

 broadest face vertical and medial; accordinglj^ there are an 

 anterior and a posterior base and also a latero-dorsal and latero- 

 ventral face, as well as a median one. The two prisms lie with 

 their axes horizontal and their median faces diverging only 

 slightly from ventral to dorsal and from posterior to anterior. 

 In contrast to the condition in Lacerta the lateral walls of the 

 cranium are more fully represented by the otic capsules and the 

 brain is confined more completely by them without exhibiting a 

 tendency to extend laterally dorsal to the capsules. On account 

 of the unusual extension of the sacculus and lagena in a ventral 

 direction the height of the capsule is almost as great as the great- 

 est length of the same. The two bases of the prismatic capsule 

 project in its long axis as a cupula anterior and posterior, the 

 latter of which is the more pronounced. The cupula anterior 

 bounds the dorsal portion of the fenestra prootica posteriorly 

 and projects freely without connection with other parts of the 

 skull. The cupula posterior bounds the fissura metotica ante- 

 riorly and laterally, extending caudally to lie external to the occi- 

 pital arch as already described. The two capsules are united 

 dorsally by the tectum posterius whose slender lateral rods arise 



