IXTllODUCTIOX. 



11 



Fig. 4. — t'lidcr view of the 

 skull of til"' cjipercJillie 

 (schizopimilionK). The 

 letters as before. 



Fig. 5, we also fiiul tlic nin.xillo-palatiiK's (i„j-p) soparalc medially an<l from tlip vomer 



(co), l)iit the latter is truiieate in front and eleft Ijeliiiid, eiiil.raeiiig the hasisiilieiioid 



rostrum (/i*) l)el\M ( ii it.s forks. Finally, the saurognathous ]>al- 



atc, which is |ieciiliar to the .sn])er-family Pieoidea?, is partieu- 



larly remarkable for having the two lateral halves of the vomer 



separate. 



It may be well, however, to state that these characters are 

 l)y no means always very trenchant, as two types often inter- 

 grade insensibly, while in t)ther eases we find them sharjily ex- 

 pressed in nearly reLitecl forms, as an e.xample of which we 

 shall imly mention the closely allied genera. Meffalaitna and 7\(- 

 raijoniipa, besides several of the birds of j>rey. 



The anterior nostrils are situated at the base of the beak 

 (except in some Struthious birds, for e.vainple, Apteri/.v, in 

 which they ojien near its ti))\ and may have a well-defined and 

 rounded hinder edge, a condition called holorhinal by Pro- 

 fessor Garrod, or be prolonged backwards as a fissure, when the 

 term schizorhinal is used. A peculiar feature of the bird's 

 be.-ik is the flexibility of its union to the frontals by the long 

 nasals and frontal processes of the ]ireinaxill;i'; this is carried 

 to an extreme in the parrots, in which the connection between 

 the beak and the forehead is formed by a movable joint. The 

 two halves of the lower jaw ancliylosc early, excci)t in some fossil forms, and the sym- 

 physis (and conseiiuently the goiiys) is of very varying length. None of the recent 

 birds have teeth in their jaws, and this negative character was a long time regarded as 



distinctive of the class, as compared with the great ni.a- 

 jority of re])tiles and mammals, liudiinentary teeth 

 have lately been denionsfrated in the grooves of the 

 lower jaw of the cmliryonic ])eng\un. It is also claimed 

 that rudiments of teeth, in sockets and covereil liy den- 

 tine, have been found in embryos of ])arrots. Late in- 

 vestigations have failed to discover the dentine. Hesicles, 

 important groujis of fossil birds have of late been dis- 

 covered, which were more or less richly sup|>lied with 

 toetli ; as, for instance, Arch<Fopter;/.r, /Aiopteri/j; (i<is- 

 toritis, Arr/illornis, Ifenperoriiis, Ichthi/ornis ; the last 

 had teeth in sockets, while those of //i'.yiiri>nii.< were 

 fixed in grooves, and were shed in a similar way to those 

 of the reptiles. 



The "saddle-shaped" vertebra is jicculiar to the bird 



class, tliat is to s.ay, the vast majority of li\ ing birils liave 



the antcsMciMl vertebrip saddle-sha[>ed, a form not seen 



elsewhere; idit opisthocielian vcrtelira' may occasionally 



even the rule ainonir the penguins, while biconcave or ampliicu-lian verte- 



Fio. 5. — t'luler viiw of ilie sl<ull of a 

 9|i.irrow iii'cithogiiatlioiis). The 

 letters as before. 



occur, iicni 



br.T, such as we find in fishes and many batrachiaus and reptiles, iiarficularly fossil forms 

 are one of the most remarkable featin-es of the extinct Arc/i"oj>t<'ri/j; Jrltthi/onilH, A/ii- 

 lornis, and, probably, Lnopten/i: The number of cervical vertebrn? varies between nine 

 and twenty-five, those of the dorsal region between four and eleven, or, exceptiotiaily, 



