704 B. W. KUNKEL 



otica by a short and comparatively slender rod, the commissura 

 praefacialis which extends dorsally and laterally from the basal 

 plate to the ventral aspect of the anterior cupula of the otic cap- 

 sule. Behind the foramen facialis the median wall of the cochlea 

 passes continuously into the basal plate along a curved line which 

 is concave on the lateral side. 



The prefacial commissure, together with the anterior cupula 

 of the capsule, forms the posterior margin of the fenestra pro- 

 otica in which is located, immediately below the capsule, the gan- 

 glion semihmare of the nervus trigeminus (g.s., fig. 7). Unlike 

 the condition in Lacerta, the gangha of the tlu'ee rami are closely 

 united so that they appear as a single gangUon wholly within the 

 fissure, except the anterior extremity which lies external and 

 ventral to the pila prootica; whereas in Lacerta the ganglion of 

 the ramus ophthalmicus lies widely separated from the others, 

 quite far in front of the slender pila prootica. 



The fissura metotica (f.m.) is a narrow slit, widening ventrally 

 to a large triangular space, situated between the otic capsule on 

 the one hand and the basal plate and arcus occipitalis on the 

 other. The otic capsule forms the anterior and lateral boundary 

 of the fissure, and the arcus occipitalis, the posterior and medial 

 one. In its narrow dorsal portion the capsule comes to lie some- 

 what external to the occipital arch so that the fissure opens nearly 

 transversely, while its extensive ventral portion faces laterally. 

 Dorsallj' the fissure is continuous with the foramen occipitale 

 magnum as already described, although its dorsal portion is 

 closed by a mass of connective tissue. 



In the expanded ventral portion of the fissure are situated the 

 nervus vagus, vena jugularis, and ductus perilymphaticus in their 

 passage to the exterior of the skull. The ductus perilymphaticus 

 occupies the extreme ventral corner of the fissure. Dorsal to the 

 ductus perilymphaticus, but still within the triangular expansion 

 of the fissure at its ventral end, are situated the jugular vein and 

 vagus nerve which in the adult pass out of the cranium through 

 the foramen jugulare externum (f.m., fig. 1). 



Beneath the canahs perilymphaticus on the left side of figure 

 2 there may be seen a narrow groove which becomes wider in a pos- 



