SKULL OF A HU]VL\N FETUS OF 40 MM. 353 



talis the latter having also a union with the capsule below the 

 capsuloparietal fissure. Dorsal to the capsuloparietal commis- 

 sure the flattened parietal plate appears, and we note that it is 

 wide ventrally, but becomes narrow dorso-medially. With the 

 parietal bone it assists in the formation of the wall of the cranium 

 in this region. Below, the parietal plate is continuous with the 

 upper border of the squama; dorsally it is represented in the 

 model as terminating freely just before reaching the dorsal 

 occipital prominence, but there is microscopical evidence, as far 

 as my sections go (as I have already stated) which seems to 

 indicate that there was here a previous union of parietal plate and 

 squama. Of the unpaired, dorso-median tectum synoticum, 

 described by several authors, I can, unfortunately, make no 

 statement, as my sections for this dorsalmost region are lacking. 

 The otic ring, as I have represented it in the model, is therefore 

 incomplete dorsally. This may possibly be its actual condition, 

 and in this connection it may be noted that Mead states that the 

 otic ring in Sus is incomplete dorsally. 



The pars otica of the lamina basalis, which is the most cranial 

 part of the chordal portion of the base of the skull, has already 

 been described. The fissura basicochlearis is incomplete above, 

 being represented by the lowermost part of what I have desig- 

 nated the spheno-cochlear notch — filled with connective tissue 

 and a few small veins. The abducens nerve passes above the 

 notch, lateral to and below the outwardly-projecting posterior 

 clinoid processes, and in this the condition is similar to that de- 

 scribed in such mammals as the rabbit (Voit) and pig (IMead), 

 except that the basi-cochlear fissure in the latter types is closed 

 above by a cartilaginous bridge joining the upper surface of the 

 pars cochlearis with the lamina basalis, the abducens nerve 

 passing over this bridge. In the model of Sus by Mead this 

 nerve passes throught a foramen formed by cartilaginous con- 

 nection of the posterior clinoid process with the cochlea. There 

 is no evidence of this in my preparation. 



The connections of the otic capsule with the planum basale, 

 squama occipitalis and parietal plate have been noted. The 

 model also shows it continuous ventro-laterally with the incus. 



