REPORT ON THE ANATOMY OF THE PETRELS. 63 



the Tubinarcs, and in all these forms it is associated with short colic caeca of peculiar 

 shape (absent altogether in the Cathartidse, as in some of the Tubinarcs), more or less 

 completely webbed feet, tufted oil-gland (except in the Cathartidge), holorhinal nostrils, 

 a tendency of the palatine bones to unite behind the posterior nares, truncated mandible, 

 broad, strong, well-developed sternum, and strongly curved, well-developed clavicles. 

 These birds also agree together in being " Altrices," the young birds being quite helpless 

 after birth, and requiring to be fed for a long time by their parents — and in generally 

 laying eggs of a white, or nearly white, colour. 



The group so constituted, of which the Ardeidge and Falconidge must also be considered 

 as aberrant members, — the first family being closely related to the Ciconiidge through 

 Scojnis, whilst the Falconidge are probably, though much more remotely, connected with 

 the Steganopods, — corresponds to the Ciconiiformes of Garrod, 1 with the addition, as he 

 had already himself suggested, 2 of the Tubinares. 



But his earlier definition of that group, in so far as it relates to the absence in it of 

 the accessory femoro-caudal muscle (B), will have to be modified, inasmuch as this 

 muscle is, as shown above, generally present in the Tubinares. These too, differ markedly 

 from the other Ciconiiformes in the well -developed pectoralis tertius (very small or 

 absent in the others), in the large size of the vomer, and the non-desmognathism of the 

 palate, though as regards this latter character it has already been pointed out that the 

 Albatrosses are nearly desmognathous, whilst the desmognathism of the Cathartidge is 

 of a different kind to that prevalent in the other forms concerned. 



The two existing groups of Petrels are clearly related to each other so much more nearly 

 than to any other group of birds that it is evident that they must have had a common 

 ancestor that possessed the peculiar features characterising the Tubinares as an order. 

 Such a form may therefore be safely assumed to have had — 



1. The characteristic nostrils of the group. 



2. The equally characteristic stomach and duodenum. 



3. Webbed feet, with a small hallux of a single phalanx. 



4. A double great pectoral muscle, and large jwctoralis tertius. 



5. A formula AB.XY, a gluteus j^rimus and an ambiens muscle. 



6. Short colic cgeca of characteristic shape. 



7. A tufted oil gland, and the pterylosis characteristic of the group. 



8. A holorhinal schizognathous skull, with large depressed vomer, great supra-orbital 

 glandular depressions, no basipterygoid facets, and a truncated mandible. 



9. A short, broad, deeply-keeled sternum, more or less entire behind, with strong 

 clavicles. 



10. A peculiar humerus, and tibia with large cnemial crest. 



1 Collected Papers, p. 213. - Lor. ci'., p. 521. 



