JIE. W. K. PAEKER ON THE OSTEOLOGY OF THE KAGU. 519 



Porphyrio. Notwithstanding the greater slendemess and inferior size of the tibia 

 of the Kagu (PI. XCI. fig. 1, t, and PI. XCII. figs. 10, 10 a, 10 5) as compared with 

 that of Porphyrio and Ocydromus^ yet the crests at its upper part (ectocnemial, ento- 

 cnemial, and epicnemial) are quite equal to what is seen in those large Kails. This 

 brings us to consider the extraordinary development of these parts in that extinct 

 Grallatorial bird which Professor Owen has called Cnemiornis (see Zool. Trans. 1866, 

 vol. V. part 5. pi. 06, p. 401). The condition of the parts in that huge type is merely 

 an exaggeration of what is seen in Porphyrio and Ocydromus, and especially, also, in 

 the Kagu. 



Both extremities of the tibia of the Kagu are large as compared with the slender 

 shaft ; the front view of the bone (PI. XCII. fig. 10) shows this, and also how closely 

 this bone corresponds with that of Cnemiornis. The lower condyles are very strongly 

 marked (PI. XCII. figs. 10 & 10 5) ; there is an oblique tendon-bridge in front, a cleanly 

 cut notch above the ectocondylar elevation, and between the two condyles there is a 

 large cotyloid cavity for the precalcaneal knob. The slender fibula (PL XCI. fig. l,fh) 

 is three-fifths the length of the tibia; the patella (PL XCI. fig. 1, l)) is rather larger. 

 The separateness of the lower articular portion of the tibia of this bird was familiar to 

 me in my early days, and the drawings made by me of these parts in the young Emu 

 twenty-four years since "are alive to testify" to this. Afterwards, when writing upon 

 the osteology of the Balceniceps (Trans. Zool. Soc. 1861, vol. iv. part 7, p. 343), I strongly 

 doubted the merely epiphysial nature of this piece, and put this question : " Is it the 

 homologue of the mammalian astragalus'?" This question has now been definitively 

 settled by Professor Gegenbaur (see his paper " Yergleichend-anatomische Bemerkungen 

 iiber das Fussskelet der Vogel," Archiv fiir Anat. u. Phys. Jahrgang 1863, p. 455). 



This apparent obliteration of the tarsal bones is a remarkable feature in the pelvic 

 limbs of the bird ; after all only two segments are found, one coalescing with the tibia 

 and the other with the three main metatarsals ; for the sesamoid bone occasionally found 

 behind the joint is not an '• os calcis," but a tendon-bone. At first sight, the tarso- 

 metatarse of the Psophia and that of the Kagu seem to have scarcely anything, except 

 the superior size of the former, to distinguish them; but there are many important 

 differences. The whole piece is much more feebly ossified in the Kagu than in the 

 Psophia, and this to a degree that is very remarkable for a Bird, reminding the observer 

 of the Penguin and of young birds generally. The ectotarsal and entotarsal keels 

 behind the upper head of the bone are only united by membrane (PL XCII. fig. 11 «); 

 they are connected by a bony bridge in Psophia : the Kagu and Eurypyga agree as to 

 the condition of these parts. 



The great " lower tarsal " is but feebly molten into the heads of the main metatarsals 

 (PL XCII. fig. 11); and these three long bones keep their sutures for a long time, and 

 have large " fenestra; " between them above — a very remarkable and interesting cha- 

 racter. There is very little trace of these spaces in Psophia, Eurypyga, Ocydromus, and 



VOL. VI. — PAET VIII. ^ ^ 



