192 MR. W. K. PARKER ON THE OSTEOLOGY 



considerable inferiority to that ot the Pigeon (PI. XXXVII. fig. 7) in the matter of brain- 

 room, the hemispheres being drawn up into a cone instead of swelling out, as they do in 

 the Pigeon, under the latter half of the tumid frontals. Nor is this all ; for, like the 

 " Struthionidae," the entire head of the Syrrhaptes is very small. I have not weighed it ; 

 but it is evident the whole head and face of the Syrrhaptes would only weigh about three- 

 fifths as much as that of a Common Pigeon, whose entire weight should be the same as 

 that of the Syrrhaptes. Notwithstanding the hkeness in the tissue of the Syrrhaptes 

 skull to that of the Pigeon, there is a great falling-ofF at the superorbital regions, as in 

 the Grouse (PI. XXXVI. figs. 2 & 7). The extremes of the Pigeon-family in this respect 

 are the Dodo and the Passerine Pigeon {Chamcsopelia passerina) ; but the latter has a 

 much more bold and rounded front than the Syrrhaptes. Every one who has an eye for 

 bird-forms must have noticed this beautiful and distinguishing feature in the Pigeon's 

 face, especially in our own native Ring-Pigeon {Columba palumbus) ; in this bird, espe- 

 cially, the egg-like roundness of the skull proper is continued undiminished along the 

 fronto-nasal region down to the hinge. The superorbital feebleness of the Syrrhaptes skull 

 coexists with a less protected condition of the eyeball in the postfrontal region. Close 

 behind the narrowest part of the frontals, the vessels of the scalp communicate freely 

 with those of the orbit. An extremely small postfrontal splint bridges over the smallest 

 " temporal fossa "(fig. 4) ; and this is in harmony with the extremely feeble condition 

 of the face, feebler even than in the small Pigeons. The Grouse peeps out here, as it 

 were, in the side of the Syrrhaptes skull ; for in Pigeons the squamosal has a much less 

 rudiment of the mammalian zygomatic process, and there is in them no bridge over the 

 temporal fossa. The os quadratum (PI. XXXVI. fig. 4) is as far from that of the 

 Grouse as it well can be, and it comes close to that of the Pluvialine birds ; but it con- 

 tains more diploe, as in the Pigeons. The homologues of the incudal crura of the 

 mammals, the heads of the os quadratum, are only short ; they have not in the least lost 

 their distinctness ; and, as in the Plovers, the peculiarly ornithic orbital process is very 

 wide and rather short : in the Pigeon it is much more pointed, and in the Grouse and 

 the Fowl it is long and styliform. The lower articular condyles of the os quadratum are 

 quite distinct (fig. 1), as in the Plover (PI. XXXVII. fig. 1 q.), and not one transverse 

 cartilage-coated surface as in the Grouse (PI. XXXVI. fig. 6) : the Pigeons generally — 

 e. g. Columba livia (PI. XXXVII. fig. 6, q.) and C. palumbus — approach the Fowl and 

 the Grouse; but the Chamaopelia has the cartilage interrupted : the Dodo agrees with the 

 typical Pigeons in this respect ; and this is very interesting, as the specialization of 

 certain structures in the Dodo's skull show it to have been the outermost leaf in the 

 Pigeon-branch of our great bird-tree. 



On its basioccipital and basitemporal aspect, the skull of the Syrrhaptes is like the 

 Grouse as to breadth (PI. XXXVI. figs. 1 & 6) ; but this breadth is much exaggerated, 

 and still the double cranial floor is not nearly so thick and spongy as in the Fowl-tribe. 

 Also the tympanic wings of the basitemporals are very thick, terminate in an angle, 



