134 MR. W. p. PYCRAFT ON THE OSTEOLOGY [Feb. 20' 



ii. The Skull of the Adult. 



The skulls of the types which form the subject of this paper 

 present no striking peculiarities or extremes of specialisation 

 such as are met with among the Eurj'ljemidpe. Yet collectively 

 they conform to one general plan distinguishable from that of the 

 Tyrannida3 and the forms which appear to me to be allied thereto. 

 This plan, and the modifications thereof, I hope to be able to 

 describe in the near future. 



The skulls of the Tracheophone Passeres, and the forms herewith 

 associated, are to be distinguished from those of the Tyrannida^, 

 Pittidje, and Philepittidee mainly on account of the absence of an 

 ossified nasal septum ; but besides these there are other small 

 characters, or combinations of characters, too subtle for tabulation, 

 but Avhich nevertheless contribute towards the delimitation of the 

 sevei-al groups. Taken separately, however, the skulls of the types 

 herein described can readily be distinguished from those of the 

 Tyranniform types. But, as will be shown in the sequel, the 

 arrangement I here propose does not rest on these characters 

 alone. 



The following are the chai'acters which distinguish the families 

 which come within the scope of the present paper : — 



Pipridce. — "With a nasal hinge ; inflated antorbital plates ; a free 

 lachrymal ; maxillo-palatine xiphoid ; vomer short a,nd broad ; 

 postorbital process obsolete ; processus zygomaticus spine-like 

 and blunt ; interorbital septum perforated. 



Formicariidce. — With anterior nares enclosed by a bony wall, 

 leaving a wide aperture at the proximal end of the nasal fossa 

 between the premaxillary and descending processes of the 

 nasal. Maxillo-palatines strap-shaped, crossing the hinder 

 end of the olfactory fossa, and passing backwards beyond the 

 level of the median, descending plate of the palatine ; vomer 

 long and broad ; postorbital process large, sometimes joining 

 the processus squamosi ; interorbital septum perforate. 



Dendrocolcqitidce. — Interorbital septum imperforate ; nostrils occa- 

 sionally of Formicaroid type ; postorbital process small ; 

 maxillo-palatines short and broad, crossing the hinder end of 

 the olfactory fossa and terminating immediately in front 

 of the descending plate of the palatine ; vomer short. 



Syncdlaxidce. — Nostrils schizorhinal ; interorbital septum perforate ; 

 maxillo-palatine of great length and slenderness and con- 

 tinued backwards to or beyond the level of the free end of 

 the median descending plate of the palatine. 

 ConojyopJiagidce. — lirteroi'bital septum wanting ; postorbital pro- 

 cesses wanting ; maxillo-palatines long, narrow, and anga- 

 lated, continued backwards to the level of the median 

 descending plate of the palatine. 

 Hylactidce. — Interorbital septum perforate ; postorbital processes 

 small, placed low down on side of skull; maxillo-palatine 

 lona; and slender ; vomer short, lono- limbs. 



