381 



The posterior section shows the termination of the cranial air-cells continued from the nasal 

 and tympanic cavities. The tympanum is divided by a horizontal partition into an upper and 

 lower chamber, intercommunicating posteriorly above the membrana tympani, which is 

 situated in the lower division, the meatus auditorius externus terminating in a narrow 

 oblique slit at the upper part of that division. The continuation of the lateral sinus with the 

 squamosal sinus is well shown in this section. The middle section shows posteriorly the two 

 tympanic chambers, and although it is taken anteriorly through the middle of the frontals, it 

 includes the whole of the rhinencephalic chamber. The extraordinary extent of the air- 

 sinuses surrounding the fore part of the cranial cavity and developed hi the orbitosphenoids, 

 the alisphenoids, the squamosals, and frontals, with the radiating bony septa of those 

 sinuses and the commencement of the attached turbinals, are shown at the fore part of this 

 section. The permanent teeth are separately displayed, with the exception of those of the 

 left ramus of the lower jaw, which are exposed ' in situ," showing the relations of the long 

 socket of the scalpriform incisor to the sockets of the molar teeth : the summits of the pre- 

 molars are unworn. 



Presented by N. Wattich, M.D., F.R.S. 



The following are parts of the same skeleton : 



2094. The atlas. 



The transverse process is perforated both horizontally and vertically by the vertebral 

 artery, which afterwards pierces the neural arch. This is deeply grooved behind, the groove 

 being almost converted into a foramen by the approximation of the posterior zygapophyses 

 or condyles. These are convex, repeating the characters of the condyles of the occiput. A 

 rough ridge extends transversely across the arch, rising into a tuberosity at its middle, and 

 dividing the outer surface of the arch into two facets. 



2095. The axis. 



2096. The five posterior cervical vertebrae. 



The last of these has its transverse process perforated. The detached articular epiphysis 

 shows that this part completes not only the end of the centrum, but an equal extent of the 

 bases of the neurapophyses. 



2097. The fifteen dorsal vertebrae. 



A deep excavation divides the metapophysis from the diapophysis of the anterior vertebrae. 



2098. The ribs of the right side. 2099. The ribs of the left side. 

 2100. The manubrium and four other bones of the sternum. 



