I'liE CHUXDJllOCKANIUM OK LEPJJDOSTJiUS. 2(31 



■ cranial wall. In Crocodilus hi^/orcatKn it h\ise.i with the otic 

 capsule at a point which corresponds exactly to the point of 

 origin of the postorbital process of fishes, and it is separated 

 from the anterior end of the crista parotica by a considerable 

 interval. The process formed, in Lacerta, by the fusion of the 

 processus paroticus with the crista parotica is said by Gaupp 

 {l. c. p. 519) to quite certainly be the homologue of the processus 

 styloideus of Mammals; and the vena jugularis and the nervus 

 facialis both run posterioi'ly beneath this process and the crista. 



In embryos of the lubbit, the crista pai'otica is said by Voit 

 ("09, pp. 449-451) to be a tall and plate-like ridge which projects 

 ventro-anteriorly from the anterior edge of the ridge of the 

 lateral semicircular canal, the anterior edge of the latter ridge 

 t)f the rabbit corresponding to the ventral edge of the I'idge of 

 lishes. Posterior to the crista parotica thei'e is said to be a 

 depression (Grube), the lower part of which is particularly deep 

 and forms a fossa subarcuata lateralis which sinks into the massa 

 augularis. This fossa must accordingly lie between the crista 

 and the ridge of the latei'al semicircular canal, iov otherwise it 

 could not sink into the massa angularis. The figures given 

 favour this interpretation of it, and it would seem to be confirmed 

 l)y the conditions in embryos of Echidna, where Gaupj) ('08) 

 shows, in figures of transverse sections, tlie crista paiotica arising 

 from the lateral wall of the otic capsule considei'ably ventral to 

 the ridge of the lateral semicircular canal and separated from it 

 by a slight depression. The upper (anterior) end of the crista of 

 the rabbit is said by Voit to " encounter " the lower (posterior) 

 end of the tegmen tympani, and then to be continued onward in 

 a slight I'idge, the crista facialis, which ends anteriorly in the 

 dorsal edge of the foramen by which the nervus facialis issues 

 from the cavum supracochleare. The latter foi-amen is called 

 tlie foramen faciale externum s. secundarium, and its external 

 opening is called the apertura tymjjanica canalis facialis. The 

 dorsal end of the hyal cartilage (Reichei't's cartilage) fuses with 

 the internal surface of the anterior (morphologically ventral) 

 etlge of the crista parotica to form the processus stjdoideus. 

 Posterior to the latter process, the processus mastoideus arises 

 from the outer edge of the crista pai'otica. Beneath the crista 

 facialis there is a groove, the sulcus facialis, which lodges the 

 nervus facialis after it issues from the apertura tympanica canalis 

 facialis, and this sulcus is continued posteriorly in the angle 

 between the crista parotica and the lateral wall of the otic 

 capsule. The crista parotica of this mammal thus has the 

 general position and relations of the opisthotic ridge of fishes, 

 rather than those of any part of the spheno-pterotic ridge, and 

 its anterior prolongation, the crista facialis, certainly does not 

 represent any part of the latter ridge. 



The tegmen tympani of the rabbit is said by Voit (I. c. p. 448) 

 to arise from the lateral surface of the but sliglitly developed 

 prominentia utriculo-ampullaris superior, tlius being related to 



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