^'o.4.] SHUFELDT ON THE OSTEOLOGY OF -SPEOTYTO. 89 



cerebellar proniiueucc and the ii[)])er mandible. It i« deepest in the 

 13arietal region. Close inspection of this area reveals minute ramifying 

 grooves for the lodgment of vessels, one set rnnning in the direction of 

 the temporal fosste and another towaids the orbits. In the " bird of the 

 year" the skull-cap is very thin and brittle in tlie dry condition; but a 

 very difierent state of affairs presenis itself when we remove a section 

 of the cranial vault from above, in the adult, where the skeleton is full- 

 grown, such as we have before us. We find exposed to our view one of 

 the common characteristics of the family ; the two tables are light, thin, 

 but compact, with a goodly supply of diploic tissue between them, at- 

 taining a thickness in some localities, notably above the exit of the olfac- 

 tories, of two millimetres or more. Owing to the large orbital cavities, 

 the brain-case is crowded to the re;ir to such an extent that the fossse 

 for the ceiebral hemispheres are situated immediately over the cavities 

 intended for the othi r encephalic lobes. We find the internal opening 

 of the foramina, already described, at the base of the brain. The jjetro- 

 sah have the appearance of two white leaves, harder than the surround- 

 ing bone, slightly turned upon themselves, with their stems leading to- 

 wards the fossa for the hypophysis. They present for examination the 

 openings for the portio dura and portio mollis, the former foramen Ijeing 

 on a lower level and anterior to the latter. In the median line running 

 from the cerebellar fossa to the exit of the first pair of nerves along the 

 roof is a raised crest, grooved on its summit for the longitudinal sinus. 

 It sinks for a little distance, in the fresh specimen, into the cerebral in- 

 terspace. The "■ sella turcica " is deep, its long axis being perpendicular 

 to a plane passing through the foramen magnum. It has at its base the 

 openings for the carotids. Immediately beyond its anterior superior 

 border is seen the niche, with its foramen at either end, for tlie passage 

 of the optic nerves and lodgment for the optic chiasma. Above the optic 

 foramina, situated still more anteriorly, is a conical pocket, pointing for- 

 wards and a little upwards, Avith the olfactory' foramina at its apex, two in 

 number, giving passage for the nerves to the orbits. The hasi-splieno'ul is 

 thoroughly united with all the bones it comes in contact with, except the 

 pterygoids, palatines, and tympanies. Its anterior process — the basi-pre- 

 sphenoid — loses itself with the vomer intheinterorbital septem,not a trace 

 remaining of the original margins of the two bones. Its wings, the orbits, 

 and the ali-sphenoids share the same fate with the bones that surround 

 them. They form the larger i)art of the posterior wall of the orbital cav- 

 ities. With the body of the bone the ali-sphenoids assist in closing in 

 the tympanic cavities. The "pterapophyjial" processes of the basi- 

 sphenoid are present ; they are short, thick, and elhptical on section, 

 crowned by facets of the same figure at their distal extremities, which 

 look downwards, forwards, and outwards, articulating with a similar 

 facet at the middle, third, and posterior border of each pterygoid. The 

 bono also presents for examination the usual nervous and arterial tbram- 

 ina and grooves for the Eastachinn tubes, the foramina being i)articu- 



