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accommodates the two thalami nervorum opticoriim, the 

 cerebellum, and nitdulla obloi.^ata, &c. On the furface of 

 the fiiperior fofla there are two flight projc Aions, produced 

 by the back of the orbits, and a fmall Ipinous rid,;e along 

 the top of the cranium, which nnarlcs the divifioii of the 

 hemifpheres ; the inferior folTa difplayi a number of de- 

 preffions, correfponding to the feveral parts it contains. 

 There are alfo two irregular projections on the fide, formed 

 by the internal organ of hearing, and anteriorly the eminence 

 called t\\e fella turcica, is to be feen, with a deep round cell 

 for lodging the pituitary gland. The depreffions on the in- 

 ternal part of the cranium are deepeft in the parrot and acci- 

 pltrine birds. 



T\iz foram'tna of ih: cranium vary in many rcfpefts from 

 what occurs in mammalia. 



The foramina through which the olfaftory nerves are 

 tranfmittcd are only two in number; they proceed from a 

 little depreffionat theanteriorpart of thefliull, and open upon 

 the upper and pollerior furface of the orbit, along the fupe- 

 rior part of vvhicli they are continued, as a deep groove, or 

 rather more than a femi-canal, to the upper and back part 

 of the nofe, where there is another foramen or flit, formed 

 by the ethmoidal bone. 



The optic foramina arife clofe together on the infide of the 

 cranium, being only feparated from each other by the thin 

 partition of the orbits ; this is frequently found deficient at 

 the pollerior part, and in that cafe the two optic foramina 

 are thrown into one. 



The fpheno-orbitar fifl'ure does not exift in birds. The 

 parts which are tranfmilted through it in mammalia, 

 pafs by diftinft holes : fome of thefe are arranged round 

 the optic foramina, and one is found on the balls of the 

 ftuU. 



The foramen rolundum s.ud foramen ovale, are fupplied by a 

 fuigle hole. It is feen on the line dividing the optic and 

 bafilar foflk. 



The canalts carotideus appears to commence far back, on 

 the outfiJe of the cranium, and iuft as it turns up to open 

 upon the filla turcica, there is a fmall foramen for the tranf- 

 miflion of the communicating branch of the internal maxil- 

 lary artery. 



The foramen hicerum anlerius does not exift, and the pofle- 

 rior foramen lacerum is fmall, and placed within and under 

 the external meatus auditorius. 



The meatus auditorius inlernus, is a very palpable foramen 

 in birds. 



The bones of the face in birds, although they differ ex- 

 tremely in form from thofe of mammalia, fl;ill preferve in 

 general a diftant analogy, by which they can be diftinguiftied 

 and compared. 



The feptum of the orbits, notwithftanding its ftrufture, is 

 fo difliniilar, muft be confidered as analogous to the ethmoid 

 bone. It is united to the os frontis fuperiorly, and to the 

 fphenoidal bone below ; it is at beft but a lamina, or plate of 

 bone, fo thin that it is nearly tranfparent\ and in numerous 

 inftanccs is in part membranous. At the back of the organ 

 of fmell there is occafionally a proccfs which projefts a little 

 from the feptum, and then turns down forming a flit, 

 through which the olfaftory nerve palFcs. This procefs 

 may be compared to the os planum, and the feptum itfelf, 

 although it is not continued far into the nofe, may perhaps 

 be thought analogous to the nafal lamdla of the ethmoid 

 bone. 



There is a bone ufually of a triangular fljape, which is at- 

 tached to the anterior, and outer angle of the os frontis. 

 This bone Cuvier has called the lacrymal, and others the 

 fuperciliary . It is in a certain degree moveable on the 



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os frontis. Its two pofteripr angles form the fuperciliary or 

 anterior edge of the orbit«. The fuptrior of them is con- 

 tinued farther backwards in the diurnal birds of prey than 

 others, giving a confidcrable prominence to the upper edge 

 of the orbit. In the oflrich, the fuperciliary arch is made of 

 a number of fmall bones, vi'hich are continued from tlic 

 lacrymal bone, and are diftinft from the os frontis. The 

 lower of the poflcrior angles of the lacrymv.l bone is pro- 

 longed confiderably in the duck, but much more in the 

 parrot, in wiiieh it goes fo far back as to join the projeftion 

 of the temporal bones, and thus completes the frame of the 

 orbit. 



The remaining bones of the face either enter into thecom- 

 pofition ot the mandibles, or are provided for the motion of 

 thefe parts. The fuperior mandible is made up of the ojfa 

 naji, rffa maxilhria, and inter maxillaria, the vomer, the malar, 

 and palatine bones ; the extremity of the man-dible appears to 

 be formed originally by a dillindl bone, which is added, as it 

 were, to all the reft. The feparate parts of the mandible are 

 not to be diftinguiftied in the adult bird, but in young fub- 

 jefts they come eafily afunder. 



The palatine bones are fo thin at their conneftion with the 

 pollerior part of the mandible, that they readily bend. At 

 the back part, tlicy fprcad out into two wings or the ptery- 

 goid procejfes, leaving a flit-(haped aperture for the pollerior 

 nares, in which is feen the vomer ; where the palatine bones 

 are joined above, there is a groove or gutter form.ed, which 

 receives the inferior edge of the feptum of the orbits, and on 

 which the palatine bones have a degree of motion when the 

 upper mandible is raifed. 



The zygoma is one of the moft remarkable parts of the 

 head of birds. It is a very long delicate bone, extended in 

 a ftraig'.it line from the inferior and back part of the upper 

 mandible to the outfide of the articular bone immediately 

 above the articulation of the lower jaw. It is, as in mam- 

 malia, originally compofed of two pieces, which in large 

 birds are always vifible. The anterior portion has been 

 commonly defcribed as a procefs of the palatine bones, but 

 it is really produced from the part of the mandible that cor- 

 refponds to the os maU or jugule, as it ought, in order to be 

 confiftent with analogy. The junflion of the zygoma to 

 the articular bone, is in a degree moveable ; this, added to its 

 general flendernefs and flexibility, allows it to yield to all the 

 motions of the fuperior mandible. 



There are two bones belonging to the head of birds, to 

 which there are none analogous in mammalia. One of thefe 

 has been called by Diimeril the fquare bone, but impro- 

 perly, as it is in no inftance exaftly fquare, and when its pro- 

 cefles are eminent, it is rather of a triangular form. AVe 

 have chofen, both from its office and fituation, to call it the 

 articular bone. 



This bone is interpofed between the articulation of the 

 lower jaw, and the os temporis ; with both of thefe it pro- 

 duces a true joint. The articular furface it prcfeiits to the 

 temporal bone, is like the two condyles of the occiput of 

 mammalia, and between thefe the end of the bone contributes 

 to the formation of the cavity of the tympanum. The 

 articular furface next the lower jaw is made ot two irregular 

 eminences, placed obliquely acrcfs, forming a double pulley. 

 On the outfide of tliis the temporal extremity of the zygoma 

 is attached, and on the infide there is articulated another 

 flender bone, which, from its fituation, defei"\'cs to be named 

 the inter-articular bone. There is a procefs from the antericxr 

 part of the articular bone, which paffes up into the orbit, 

 and receives the attachments of mufclcs. 



The inter-articular bone is connected by a moveable joint 

 to the articular. It is a fmall, ftraight, three-fldcd bone, 



llighily 



