PROFESSOR OWEN ON CNEMIORNIS. 269 
in Tachyeres*. A second small vacuity weakens the ilium above the hind part of the 
ischiadic foramen in Tachyeres, as in the White-eyed Pochard (Anas leucophthalmus)? ; 
but this character is not present in Cnemiornis or in Cereopsis. The proportion in 
length of the preacetabular to the postacetabular parts of the pelvis is greater in the 
two last-named genera than in Zachyeres. 
I have nothing to add to the characters of the femur, tibia, and fibula illustrated in 
my former memoir. The excessive development of the combined pro- and epicnemial 
processes, which suggested the affinity or resemblance to Colymbus, we now know to have 
been possessed by a species of another family of web-footed birds. The great extinct 
Anserine of New Zealand may have kicked its way through the dense element with a 
vigour and speed that would have arrested the attention of navigators more strongly, 
perhaps, than such action in the smaller non-volant Lamellirostral which has thereby 
got the name of “Steamer Duck.” 
The three digits whose metatarsal bones coalesce to form the “ metatarsus ” in birds 
are homotypes of the three metacarpals similarly fused together in the wing, viz. the 
second, third, and fourth. ‘The first, sometimes wanting, but more commonly present, 
keeps its rudimental metatarsal element free in all species with the back toe. The 
rough slightly depressed surface above the entotrochlea shows the usual anserine posi- 
tion of attachment of the back toe in Cnemiornis. 
The metatarsus of Cnemiornis (Plate XX XVIII. fig. 12) yields well-marked evidence 
of its closer affinity to Cereopsis than to Tachyeres or other Lamellirostral genera. In 
these the entotrochlea, or that distal condyle which supports the second or innermost * 
of the three anterior toes, is given off from the composite bone at a higher or more 
proximal level than the other two trochlear condyles (ib. fig. 14, 11): it also projects 
much more backward than the other condyles. In Cereopsis the entotrochlea (ib. 
fig. 13, 11) comes off at a lower level, nearly that of the ectotrochlea, and projects but a 
short way behind the line attained by the hind part of the mesotrochlea, this terminating 
a little behind that reached by the ectotrochlea. Thus, in Cereopsis, the three trochlez 
are more in accordance with the ordinary pattern in non-natatorial birds; and this is 
precisely the character by which Cnemiornis departs from the web-footed order in the 
' According to Mr. Smit’s figure of the pelvis of the Steamer Duck in Trans. Zool. Soc. vol. vii. pl. 62. fig. 59 : 
the originals, collected at the cost of the nation in a Government expedition, have not found their way to the 
National Museum of Natural History. On special application to the naturalist of the expedition of H.M.S. to 
the Magellan’s Strait, some bones of an immature Tuchyeres have been sent by him to the British Museum since 
the penning of the present paper. 
2 Nyroca, Flem.; see Eyton, ‘ Monograph on the Anatide,’ 4to, 1838, p. 63, and plate. 
3M. Alphonse Milne-Edwards, describing the metatarse of Cereopsis in his ‘Recherches pour servir 4 
Vhistoire naturelle des Oiseaux Fossiles,’ 4to, 1867, writes of the “ trochlées digitales :’—“T’externe, au lieu d’étre 
fortement rejetée en arriére, comme dans les autres Anatides; se trouve presque sur le méme plan que la 
médiane” (p. 80). I find the “ ectotrochlea ” (supporting the, outer five-jointed toe) to have its hind border a 
little anterior to the plane of that of the mesotrochlea, while the entotrochlea projects as much behind that 
plane, but in a markedly less degree than does the internal trochlea in Tachyeres and other Anatide. 
VOL. 1X.—ParT 11. May, 1875. 20 
