708 B. W. KUNKEL 



capsular wall the prominences of the anterior and posterior semi- 

 circular canals unite with the dorsal end of the prominentia sinus 

 superioris utriculi. 



The prominentia semicu-cularis lateralis with that of its am- 

 pulla forms a horizontal ridge which is situated on the lateral 

 sui-face of the capsule between the ventral ends of the anterior 

 and posterior canals, and which broadens anteriorly to accom- 

 modate the ampulla. A decided triangular depression marks this 

 ridge off dorsallj^ from the other two canals. Ventrally it passes 

 gradually into the prominentia saccularis except at its anterior 

 end where the prominentia recessus utriculi is situated. 



The prominentia recessus utriculi on the lateral aspect of the 

 otic capsule occupies a circular space ventral to the combined 

 prominences of the ampullae lateralis and anterior, dorsal to the 

 foramen facialis, and antero-dorsal to the fenestra vestibuli. 

 On the median face of the capsule it forms a gentle triangular 

 convexity with its posterior angle situated immediately dorsal 

 to the foramen acusticum posterius; its antero-ventral angle 

 dorsal to the foramen facialis and anterior to the foramen acus- 

 ticum anterius. The prominentia recessus utriculi is separated 

 above from that of the anterior semicircular canal by the shallow 

 fossa subarcuata; it passes imperceptibly into the prominentia 

 ampuUaris anterior in front, and is boimded ventrally by a line 

 joining the foramina facialis and acusticum posterius; it is con- 

 tinued posteriorly between the latter and the foramen endolym- 

 phaticun\ and forms a marked convexity for the ductus endolym- 

 phaticus immediately dorsal to its opening into the sacculus, and 

 ventral to the foramen endoljauphaticum. 



The prominentia sinus superioris utriculi extends obUquely 

 antero-dorsally iron) the foramen endolymphaticum to imite 

 with the dorsal ends of the prominences of the two vertical semi- 

 circular canals. In front it forms the posterior boundary of the 

 fossa subarcuata, posteriorly it is continuous with the combined 

 prominentiae utricularis and ampullaris posterior. 



The prominentia saccularis occupies the entire ventral third 

 of the capsule. In contrast to the condition met with in most of 

 the vertebrates, the cochlea of the chelonians extends posteriorly 



