HEMISECTION OF THE SKULL. 187 



O. ip., Os interparietale, az. — Interparietal bone. 



O. boc, Os basioccipitale, az. — Basioccipital bone. 



O. pro., Os perioticum. — Periotic bone (Fig. 59). 



O. bsph., Os basisphenoideum, az. — Basisphenoid bone. 



O. temporale. — Temporal bone. 



O. parietale. — Parietal bone (Fig. 56). 



O. pt., Os pterygoideum. — Pterygoid bone. 



O. alsph., Os alisphenoideum. — Alisphenoid bone. 



O. pit., Os palatinum. — Palate bone (Fig. 57). 



O. orsph., Os orbito-sphenoideum. 



O. frontis.— Frontal bone (Fig. 56). 



§ 548. O. vomeris, az. — Vomer. — The vomer is a mesal bone forming part of tte 

 septum of the nasal cavities. 



§ 549. O. mesethmoideum, az. — Vertical plate of the ethmoid. — This is a mesal bone 

 forming most of the partition between the nasal cavities. 



O. Nasale. — Nasal bone. 



O. mxtrb., Os maxillo-turbinale — Maxillary or inferior turbinated bone. — It is a 

 greatly plicated bone occupying the ventral p at of the nasal cavity. 



§ 550. O. ethtrb., Os ethmo-turbinale — Ethmo-turbinal bone. — This is also a greatly 

 plicated bone ; it occupies the dorsal and greater half of the nasal cavity. It projects 

 caudad into both the frontal and the sphenoidal sinuses (Fig. 60). 



O. pmx., Os praemaxillare. — Praemaxillary or intermaxillary bone (Pig. 57). 



O. mx., Os maxillare — The upper jaw bone. — In this figure it is not marked, but it 

 is the deeply shaded part just caudad of the 0. Prmx. 



Pre. pel., Processus postclinoideus, az. — Posterior clinoid process. 



Pre. prcl., Processus praeclinoideus, az. — Prseclinoid process. 



Sella, Sella turcica, az. — This is a space or pit formed by the two clinoid processes 

 (Fig. 88). 



§ 551. S. sph., Sinus sphenoidalis — Sphenoidal sinus. — This is a space in the prae- 

 sphenoid bone. It is separated from its platetrope by a bony partition. It is lined by a 

 continuation of the nasal mucous membrane, and communicates freely with the nasal 

 cavity. 



S. frn., Sinus frontalis. — Frontal sinus (Fig. 56, 60). 



§ 552. Tent., Tentorium. — The osseous tentorium cerebelli is a moderately thick 

 plate of bone projecting from the parietal bones into the cranial cavity ; it separates the 

 cerebrum from the cerebellum (Fig. 88). 



Each parietal bone furnishes half of the tentorium, and its halves are conjoined at the 

 meson by a ventral continuation of the sagittal suture ; (see Fig. 88). 



§ 553. Fig. 60— Preparation. — The skull was divested of its soft 

 parts (§ 250, B). It was then sawed obliquely across its cephalic 

 half so as to include the optic foramina, and to fully expose the 

 frontal sinuses. The left lateral wall of the olfactory fossa was 

 nipped away, and likewise the lateral projections of the maxiUa. 



Cn. Ich., Canalis lachryraalis.— Lachrymal canal (Fig. 56). 



Fm. (Foramen) opticum — Optic foramen. — The optic chiasma rests in the groove 

 between the two foramina (Fig. 114). 



