262 Mtt. E. 1'. ALLis OX The otIc region oj<' 



the anterior (superior), instead of tlie lateral semicircular canal. 

 It is said to project laternlly and upward as an arched umbrella- 

 shaped roof (" leicht gewolbtes schirmfurmiges Dach), and also to 

 extend forward a cei'tain distance, there arching over the nerviis 

 facialis and, beyond tliat nerve, fusing with the pars cochlearis 

 of the otic capsule, along the lateral edge of the planum 

 supracochleare ; thus forming the lateral Avail of the cavum 

 supracochleare, the ventral portion of which is perfoi*ated by the 

 foramen faciale externum s. secundarium. That part of the 

 tegmen that lies anterior to this foramen is said (I. c. p. 533) 

 to correspond to the freely projecting processus perioticus 

 superior Gradenigos of certain other mammals, and to be 

 continued anterioi'l}' a certain distance by procartilaginous tissue 

 which later chondrities. The commissura capsulo-parietalis fuses 

 with the dorsal surface of the umbrella-shaped tegmen tjunpani, 

 and it is that part of the tegmen that lies ventro-mesial to the 

 line of this fusion that forms the lateral wall of the cavum 

 supracochleare, the part that lies lateral to the line of fusion 

 forming a tall ridge which projects ventro-laterally and extends 

 posteriorly slightlj' beyond the anterior end of the crista parotica, 

 where it curves ventrally to meet the basal poi-tion of that crista. 

 This ridge, alone, is frequently referred to in the text as the 

 tegmen tympani, and it is it alone that is so designated, in 

 the figures, by the index letters. The fossa that lies between 

 this ridge and the crista facialis is called the fovea epitympanica, 

 and its posterior portion is said to be deepened to form the fossa 

 incudis, this latter fossa lying, as shown in the ligiires, on the 

 external surface of the otic capsule, while the anterior portion of 

 the fovea ei^itympanica lies upon the external surface of the 

 lateral wall of the cavum supracochleare. The tegmen tympani 

 is said to be a direct anterior prolongation of the ci'ista parotica, 

 but one is in doubt as to whether this apjjlies to that part of the 

 tegmen that forms the mesial wall of the fossa epitympanica 

 or the part that forms its roof. The crista facialis is also said, as 

 above explained, to be a direct anterior prolongation of the crista 

 parotica, ami yet this crista is simply a ridge on the external 

 surface of that part of the tegmen that forms the mesial wall of 

 the fovea ejjitympanica. 



Yan Kampen ('05 j, in a,n earlier work, gives a somewhat 

 different description of the tegmen tympani of Mammals in 

 general. According to him (I. c. p. 344), Reichert's cartilage 

 fuses with a cartilaginous ridge which arises from the outer 

 surface of the ridge of the lateral semicircular canal. Anterior 

 to the point of this fusion, the ridge separates into two parts, 

 one of which is called by Van Kampen the crista facialis, and 

 corresponds to the similarly named crista of Voit's descrij^tions 

 of the rabbit. The other part of the ridge is said to lie at a 

 higher level than tlie crista facialis, and the two ridges enclose 

 between them a pai'fc of the wall of the pars vestibularis of the 

 otic capsule which Van Kampen calls the mesial wall of the 



