258 PEOFESSOR OWEN ON CNEMIOENIS. 



The prefrontals (PI. XXXV. fig. 12, 14), perforated in Birds', as in all other vertebrates, 

 by the olfactory nerves, expand from their coalescence with the presphenoid (ib. fig. 4, 9) 

 to articulate above with the fore part of the frontals and to give support to the lacrymals. 

 They form the fore part of the rhinencephalic cavity, and contribute to the hind part 

 of the walls of the olfactory cavity, of which they there commence the " septum," by 

 their mutual coalescence. 



Each olfactory nerve passes from the rhinencephalic to the olfactory chamber by a 

 single canal (fig. 12, ol), the right and left nerve forming a pair separated by the 

 base of the " septum," and indicating the primitive quality of the neurapophyses of 

 the third cranial vertebra (ib. u). 



The frontals are truncate anteriorly (ib. fig. 3, ii, ir) and present two transversely 

 elongate convexities or condyles (fig. 11, A, h) for articulating with the nasals ; external 

 to which junction the nasals (fig. 3, is) expand slightly to form a convexity (fig. 12, l) 

 articulating with a concavity at the fore part of the base of each lacrymal. A pair of 

 short fine fissures (fig. 3, 22) indicate the proportion which the premaxillary contributes 

 to the naso-frontal joint. 



A similar indication in Cereopsis (ib. fig. 8) bespeaks a relatively broader nasal process 

 of the premaxillary. The bifurcation of the nasal at a, h (figs. 1, 3, 6, 8) to form the 

 hind border of the external nostril has the angle rounded at the apex in Cnemiornis 

 (fig. 1, n) ; it is notched and irregular in Cereopsis (fig. 6, n) ; the nostril is large 

 and ovate in both, but with the anterior end larger and more definitely marked 

 and rounded in Cnemiornis. 



The intemarial tract of the upper mandible is almost flat in Cnemiornis (fig. 3, c), 

 but is convex, i-aised into an arch, in Cereopsis (fig. 8, c). The definition of the broad, 

 short, rostral part (figs. 1, 3, 6, 8 d) of the premaxillary is well defined in both ; but 

 the defining channels at the sides of the base of such rostral part are deeper, and are 

 bounded by a ridge behind, in Cnemiornis. The " rostrum " is pitted by the usual 

 vascular impressions and foramina relating to renewal of the horny beak-sheath in both 

 Anserines. 



On the bony palate a median " prepalatal " a acuity exposes the anterior extremity of the 

 vomer (fig. 4, 13) at a higher level. At a lower one, behind the vacuity, is the orifice of 

 a longitudinal " palato-vOmerine " canal (figs. 4, 11, e), running backward between the 

 bony palate and the vomer. The prepalatal vacuity is represented in Cereopsis by a 

 depression (fig. 9, is), into the back and deep part of which the palato-vomerine canal 

 (ib. e) opens. The extent of median coalescence of the palatal plates of the maxillaries 

 ( 1 if this be not due to the vomer), behind the palato-vomerine foramen, is relatively 

 the same in Cnemiornis and Cereopsis. 



The palatal vacuity is present in Tachyeres Irachypterus and most Lamellirostrals, is 

 largest (so far as I have seen) in Carina moschata, is reduced to a fissure in some 



