gQ PEOF. W. K. PAEKER ON THE 



plaster. There is a small hole between the middle and inner metatarsals near the top. 

 The lower condyles of the shank agree very closely with those of Crax, but the tarso- 

 metatarsus differs from that of the Curassow in its flatness, from side to side, and in the 

 deo-ree of concavity of the anterior outline. The condyle for the fourth digit is 

 quite Cracine, being somewhat grooved, and having an outer process, which reaches a 

 considerable distance backwards. In Corythaix this condyle is slightly grooved, but 

 the inner half is larger, and that bird has a mobile outer toe. There is very little 

 difference, in Ojnsthocomus, between the proximal and penultimate phalanges. The 

 hallux, or first digit, is larger than in the Megapodidae and Cracidse, and its claw is 

 the largest of the four, as I have shown in the 1st stage (PI. VII., dcjJ) ; thus the foot 

 of this bird is truly Insessorial ; it is more of a Percher than its nearest relatives, the 

 Curassows. 



IX. Recapitulation and Summary. 

 a. The Ornithological Position of Opisthocomus. 

 The existing Carinate birds are extremely hard to classify ; we are embarrassed with 

 the riches of this great Avifauna; but there is one clue that can be used, namely that 

 the fewer there are in any family the more archaic that family is, and vice versa. The 

 Ratify have acquired their distinguishing character ; it is evidently not primary. The 

 Tinamous and the Hoatzin are, in many respects, as archaic as the Eatitse ; in some 

 more so. If the term Dromseomorphse is to be retained, let it take in the Eatitae and 

 the Tinamidae. Next to that group would be the AlectoromorphaB, and the lowest of 

 these would be Opisthocomus — the Opisthocomidse ; the highest the Columbidse : that 

 group would also take in the Pteroclidse, which lie under the Pigeons. 



Here, also, between the Tinamous and the Quails, would be placed the Turnicidge 

 (not to be called Turnicomorphse — that term is too general). Then, on the other 

 side of the class, the Cypselomorphge and the Psittacomorphas should be melted into 

 the common mass with the rest of the Coccygomorphae ; we should thus get an Order 

 to compare with the Coracomorphse, as variable as that Order is uniform. Ornitho- 

 logists must understand that terms taken from the anatomical structure of birds are 

 not ornithological; they are morphological terms, which the Ornithologist uses for 

 taxonomic purposes. Sometimes they are of very little value ; at other times they can 

 be applied to large assemblages of birds. Thus Prof. Huxley's term ^githognathae is 

 of o-reat value ; the only Family outside the great Passerine group (Coracomorphae) 

 which has that peculiar modification of an open or schizognathous palate is the Cypse- 

 UdiB. Thus the morphological term iEgithognathae can be nearly superimposed upon 

 the ornithological term Coracomorphae. But the term Desmognathae has no such wide 

 use, nor the term (one of my own coining) Saurognathae ; the Toucans are Desmo- 

 gnath«, the Woodpeckers are Saurognathae ; yet these two groups are closely related. 

 In the present state of our knowledge Taxonomy is a very tentative science ; it is only 



