SKULL OF THE EZGITHOGNATHOUS BIRDS. 263 
hooks (mz.p) are simpler. The inferior submarginal sulcus of the vomer evidently 
here also marks off a distinct septo-maxillary (s.ma)'. 
Example 38. Skull of Dendreca pennsylvanica. Family Mniotiltidee. 
Section Oscines. 
Habitat. Panama. 
These forms come very close to the last, but also somewhat nearer to the proper Notogveal 
types. The leafy part of the transpalatine (Plate XLVIII. fig. 1, ¢.pa) is very abortively 
developed; the postpalatine keels are well developed; the transverse isthmus is broad, 
the interpalatine spike (i.pa) large, the ethmo-palatine (¢.pa) broad, and the prepalatine 
bar (pr.pa) very long and slender. The maxillary is completely united to the pre- 
maxillary and jugal; and the maxillo-palatine (ma.p) is an elegant decurved spatula, 
with a small “keel” and a large external open air-cell. The vomer (v) runs into the 
ethmo-palatine below; it is large, subcarinate laterally, sulcate below; and the part 
beyond the sulcus is manifestly a long septo-maxillary (s.mzv) pointed behind and 
bilobate in front. The bony mass formed by these two pairs of bones is freely grafted 
upon the inturned lamina (7. a. 7) in the usual manner. The whole nasal capsule agrees 
very closely with what has been described in Sericornis and Sittella ; but the recurrent 
cartilage (re.c) is unusually large. Besides the lesser transpalatines, this type has 
another character distinguishing it from the Australian forms: it has a delicate palato- 
maxillary style (p.m) on each side of the prepalatine bar. I have already shown that 
this bone exists in the Tanagride and Brachypodide, and shall soon describe it in other 
families. Outside the Coracomorphe I have only seen it in the Celeomorphe (Picide 
and Yungide) ; and in them it only occurs on the /ef¢ side (Trans. Linn. Soc. 1875, ser. 2, 
Zool. vol. i. pls.i—v.). In Dendreca I find neither lacrymal nor os uncinatum. The ecto- 
ethmoid is specialized further than it is in the Australian forms; for a bony bridge sepa- 
rates the passage for the olfactory from that of the orbito-nasal nerve. 
Example 39. Skull of Mniotilta varia. Family Mniotiltide. Section Oscines. 
Habitat. Panama. 
The palate of this bird is almost precisely like that of Dendraca; even in the minutest 
details this is seen (Plate XLVIII. fig. 2). One description may serve for both. 
‘ The rapid development and early ankylosis of bony centres in birds makes the study of their osteology very 
difficult; also the breaking-off of a projection of a primary centre to make a new bone, as in the mesopterygoid. 
I am in some doubt whether this lateral piece of the tetramerous yomer of the type now being described is not 
formed in this way. Perhaps, also, in some cases, the distinct “ palato-maxillary” may be the palatine process 
of the premaxillary detached ; Ihave, however, no proof of this ; and that process is very apt to become absorbed 
when no palato-maxillary appears. It would be sure to be removed if a new centre came behind it to take its 
place. 
