MR. W. K. PARKER ON THE OSTEOLOGY OF THE KAGU, 519 
Porphyrio. Notwithstanding the greater slenderness and inferior size of the tibia 
of the Kagu (Pl. XCI. fig. 1, 4, and Pl. XCII. figs. 10, 10a, 1006) 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 Rails. ‘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. pl. 66, 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 (Pl. XCII. fig. 10) shows this, and also how closely 
this bone corresponds with that of Cxemiornis. The lower condyles are very strongly 
marked (Pl. XCII. figs. 10 & 10); 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. XCL. fig. 1, £2) 
is three-fifths the length of the tibia; the patella (Pl. XCI. fig. 1, p) 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 Baleniceps (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 “ Vergleichend-anatomische Bemerkungen 
iiber das Fussskelet der Végel,” Archiv fiir Anat. u. Phys. Jahrgang 1863, p. 495). 
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 a); 
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 “fenestre” 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.—PART VIII. 40 
