56 PEOl'. W. K. PAEKEK ON THE 



The superficial or somatopleural elements of the mandible are very stout, but quite 

 normal ; the largest is the dentary (PL VII. & PL VIII. fig. 2, d.) ; it is closing in upon 

 IMeckel's cartilage in the 3rd stage, and that rod is beginning to shrink ; the splenial 

 (PL VIII. fig. 2, sp., deflected in the figure) is long and thin ; the coronoid, as in the 

 Fowl tribe and some others, is absent ; and the supra-angulare (s.ag.) and the angulare 

 (ag.) are normal, and are at present quite distinct from, and superficial to, the 

 articulare (ar.). The skull of the adult is very solid and strong \ and does not suggest 

 a Musophagine relationship so much as the younger and feebler specimens ; both in 

 the skull and general skeleton it will be necessary for me to give some account of the 

 parts in the adult, notwithstanding the excellent desciiptions already given by Prof. 

 Huxley, for I wish to make my own monograph complete ; moreover my observations 

 have been made from a somewhat diflerent standpoint. The skull of Opisthocomus is 

 remarkably short, stout, and broad ; the bill, when the mouth is closed, is almost 

 conical ; it is much unlike that of the Peafowl, which is more arched and is very 

 lightly built. The likeness to that of the Musophagidse (e. g. Corythaix buffoni) is 

 much less in the old male than in the feebler specimens ; but the skull of those 

 Ethiopian Cuculines resembles that of the Cracidse, and they seem to have something 

 Gallinaceous in their nature ; they might be called Cracine Cuckoos. The true 

 Cuckoos of the Neotropical Region {Saurothera, Geococcyx, and Piaya) are the proper 

 isomorphs, not relatives of the Cracidse. In Opisthocomus the rostrum is, measured 

 in a straight line, two-thirds the length of the cranium proper ; the lower edge is 24 

 millim. in extent, and the culmen, measured along its curve, 30 millim. This part is 

 hinged on to the cranium at a considerable angle, so that if a line be drawn from the base 

 of the quadrate to the point of the rostrum, the fore end of the jugal bar would be 

 8 millim. above that line. This general deflection of the rostrum and the arched form 

 of the mandibles, whose lower edge rises 5 millim. above a basal line, gives a stunted 

 and strong appearance to the face of this bird ; it is short-faced even for a Fowl. The 

 likeness of this skull to that of a Touraco (Corythai-x) will be illustrated by the 

 following measurements : — 



In the large Crax gloMcera the skull is twice as long as in the two birds just com- 

 pared together ; its hinge is 20 mUlim. across, but it is all ankylosed except the 



' In the Hunterian Museum there are two skeletons of this bird ; these will be referred to here as A & B. 

 The mounted specimen (A) is evidently that of an old male bird ; the other is an injured specimen, and is not 

 mounted. Prof. Huxley's figures (P.Z. S. 1S6S, pp. 310, 311, figs. 13-16) show feebler birds, and wore 

 probably younger specimens or females. 



