MK. W. K. PAEKEE OX THE OSTEOLOGY OF THE KAGU. 517 



scapula of the Skate ('Shoulder-girdle and Sternum,' pi. 1. figs. 1-4, sc. (.-). The 

 great backward extension of the ilium in the bird is illustrated by the large, flappy 

 suprascapula of the Lacertians {op. cit. pis. 9-11, s.sc); in the Rhea, and in a less 

 degree in the Apteryx, the ilium stops short of the ischium behind. The manner in 

 which the three main elements of the " os innominatum " meet in the " acetabulum " is 

 beautifully illustrated in the shoulder-girdle of the Batrachia, especially in Dactyletkra 

 (oj}. cit. pi. 6. fig. 11). The pehic counterpart of the great notch between the supra- 

 scapula and scapula above and the coracoid below is filled up behind in most birds by a 

 continuous growth of cartilage, so that we have not an ischiadic " notch," but a large 

 "fenestra." In the Skate (o^j. cit. pi. 1. fig. 2, sc.f, cr.f) there are two fenestra in the 

 corresponding region of the shoulder-girdle moiety. In the Apteryx, the Emu, the 

 Cassowary, the African Ostrich, and the Tinamous (Trans. Zool. Soc. 1864, vol. v. part 3, 

 pi. 39, il,isc) this space is open in the same manner as in the shoulder-girdle of the 

 Frog. In Dacti/lethra, in the Chelonians, and in the African Ostrich the space be- 

 tween the precoracoid and coracoid (the countei-parts of the pubis and ischium in the 

 pelvis) is a large, deep notch (' Shoulder-girdle and Sternum,' pi. 6. fig. 11, pi. 12. fig. 2, 

 and pi. 17. figs. 5, 6). In birds, generally, the " obturator" space is a very deep notch ; 

 in the Rhea it is a huge "fenestra" from the first; in the Buceiidae it becomes so by 

 coalescence of the pubis with the ischium ; these differences are all in harmony with 

 what is seen in the various conditions of the shoulder-girdle. The moieties of the 

 hip-girdle only meet below and coalesce in the African Ostiich ; in other birds they 

 keep apart; in the Toad (op. cit. pi. 5. figs. 15-17) the counterparts of the pubes meet 

 and coalesce, this being, however, an exceptional condition as to the Batrachia, and 

 borrowed from the Skate and Shark (op. cit. pi. I. figs. 1—4). 



In certain Fishes the scapular region becomes segmented from the coracoid (oji. cit. 

 pi. 2. fig. 12, sc, ])cr) ; in certain Amphibia, as in some other fishes (e. g. Trigla, Agonus, 

 Goiius, op. cit. pi. 2. fig. 13), this connectivum is only partially separated; this partial 

 separation appears again in the rudimentary cleft seen in the fundus of the glenoid 

 cup in Proteus and Cryptobranchus {op. cit. pi. 3. figs. 1 & 3, gl). 



In birds the pelvic counterpart of this cleft is constantly present, and its large size 

 and irregular shape is well illustrated in Professor Owen's paper on Cnemiornis (Trans. 

 Zool. Soc. 1866, vol. v. part 5, pi. 64. fig. la). 



Hence it will be seen that the hip-girdle is the same in its morphology as the 

 shoulder-girdle, that in the Class of Birds its spinal crest is hugely developed but per- 

 fectly normal, and that the whole of each moiety is a cartilaginous plate superadded to 

 the axial skeleton and tending to undergo fission in exactly the same manner as the 

 shoulder-girdle moiety. Also it is evident that the hip-girdle is always of a lower 

 morphological type than the shoulder-girdle, its fission and general metamorphosis 

 being so much more arrested in the same individual type ; so that, whilst the shoulder- 

 girdle of the Skate illustrates the hip-girdle of the Bird, the hip-girdle of the Mammal 



