SKULL OP THE ^GITHOGNATHOUS BIRDS. 263 



hooks (mx.p) are simpler. The inferior submarginal sulcus of the vomer evidently 

 here also marks off a distinct septo-maxillary (s.nuvy. 



Example 38. Skull of Dendrceca peimsylvanica. Family Mniotiltidse. 



Section Oscines. 

 Habitat. Panama, 



These forms come veiy close to the last, but also somewhat nearer to the proper Notogjeal 

 types. The leafy part of the transpalatine (Plate XL VIII. fig. 1, t.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 [e.pa) broad, and the prsepalatine 

 bar [pr.pa) very long and slender. The maxillary is completely united to the prae- 

 maxillary and jugal ; and the maxillo-palatine (nis.j}) is an elegant decurved spatula, 

 with a small " keel " and a large external open au--cell. The vomer (y) 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.mx) pointed behind and 

 bilobate in front. The bony mass formed by these two paii's of bones is freely gi-afted 

 upon the inturned lamina {i. a. I) in the usual manner. The whole nasal capsule agrees 

 very closely with what has been described in Sericomis and Sittella ; but the recurrent 

 cartilage {rc.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.mx) on each side of the prsepalatine bar. I have already shown that 

 this bone exists in the Tanagridse and Brachypodidae, and shall soon describe it in other 

 families. Outside the Coracomorphse I have only seen it in the Celeomorphse (Picidae 

 and Yungidae) ; and in them it only occurs on the left side (Trans. Linn. Soc. 1875, ser. 2, 

 Zool. vol. i. pis. i.-v.). In Bendrmca 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 Mniotiltidae. Section Oscines. 



Habitat. Panama. 



The palate of this bird is almost precisely like that of Dendrceca ; even in the minutest 

 details this is seen (Plate XL VIII. 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 vomer of the type now being described is not 

 formed in this way. Perhaps, also, in some cases, the distinct " palato-maxUIary " may be the palatine process 

 of the praemaxillary detached ; I have, 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. 



