58 PEOF. W. K. PARKER ON THE 



their habits, and in both families the foot is flat. They are Peristeropodous, not high- 

 heeled as the other true Gallinaceae, which are Alectoropodous (see Huxley, P. Z. S. 

 1868, pp. 294-819). The palatal region of Opisthocomus as a whole would have been a 

 very difficult study if the Tinamou had not come in for our enlightenment. It is only 

 by tracing the relation of the latter type as well as of Opisthocomus to the Struthious 

 forms that we shall find the real clue. 



When we come to the organs of flight it will appear evident that both these low 

 Neotropical Families show good proof that they are much less modified from the ideal 

 archaic bird than the Katitse, which have manifestly undergone a large amount of 

 degradation on the one hand and specialization on the other. 



In the general palatal view (Huxley, op. cit. p. 311, fig. 16) ^ the skull of the adult 

 is more Struthious than in the embryo (PI. VIII. fig. 1), for the long ascending 

 processes of the palatines meet at no part, and behind the sharp vomerine wedge the 

 rostrum of the parasphenoid is exposed. The pterygoids behave in this type as they 

 do in the Tinamou, in both of which the mesopterygoid is segmented off and unites 

 with the palatine, as in the majority of birds; in the Eatitse there is no segmentation, 

 and no special modification of the fore part of the pterygoid. In Fowls proper, as in 

 the Goose tribe, that part becomes a neat peg which rolls in a groove on the upper 

 and hinder face of the palatine. The slight development of the hinder part of the pala- 

 tines, and the extreme feebleness of the fore part, are essentially general or Struthious ; 

 so also is the imperfect development of the maxillo-palatines, and the length and 

 breadth of the vomer. That bone is not so Struthious as it is in the Tinamou, but is 

 intermediate in size between the vomer of that bird and that of the Fowls proper, in 

 which it is, as a rule, a slender azygous style. Its breadth and forked form suggest a 

 primary division of the bone in Opisthoconius, although, as I have shown, my earliest 

 embryos have it already in one piece. In my earliest embryo of Sfruthio camelus 

 (Phil. Trans. 1866, pi. vii. fig. 4, v.) it was, although very large for a bird, in one piece. 

 The proper pterygoid segment of the adult is remarkable for its dilatation in front ; it 

 wants the neatness seen in the higher kinds of birds, and the dilatation, which is great 

 and reptilian in the Eatitse, is nearly equal in this bird to what is seen in the Penguins. 

 The quadrate is not like that of a typical Fowl, or of a Tinamou, or of a struthious 

 bird ; in these latter, as a rule, and in the Tinamou, the otic process is oblong and 

 undivided ; in the Fowl there is a round main condyle and a small secondary head on 

 its inside. But in the Cracidse and Megapodidae the head is divided into two condyles, 

 the outer larger than the inner in Cr^ax, but the two are subequal in Talegalla ; in 

 Opisthocomus they are subequal as in the latter bird ^. 



^ In this figure the basitemporal is shown as abortively developed, or it was injured on one side ; it is 

 perfectly symmetrical in the Hunterian. specimen (A), in which both of the Eustachian tubes are well floored. 



- In working out the Apteryx, my son, Prof. T. Jeffery Parker, finds that its quadrate has its otic process 

 undivided, as in the Cariuatce generally. This is a remarkable fact, as the whole upper face of that bird is 

 perhaps mure immobile than in any other type in the Class. 



