ALC^ 339 



ALC^ 



Definition. — Oil gland tufted. Aftershaft present ; aquincubital. 

 Skull sohizognathous and sohizorhiual. Occipital fontanelles 

 present, but no basipterygoid processes. Two carotids.' Ten- 

 sores patagii and biceps slip distinctive. Uo expansor seoun- 

 dariorum. Dorsal vertebrse opistlioocoelous. 



This group of birds comes nearest to the Limicolae, but 

 differs more from any of them than they do among them- 

 selves. The group is entirely confined to the northern 

 hemisphere, and is mainly Arctic. 



The oil gland is invariably tufted and the feathers have an 

 after shaft. 



In the pterylosis the dorsal tract divides between the 

 scapula, and there is (? universally) a well-marked spinal 

 space. But there is no break between anterior and posterior 

 parts (as in Limicolae). The ventral tract, contrary to what 

 we find in the Limicolae (incl. Laridse), does not divide early 

 in the neck. The rectrices (see table, later) vary in number 

 from twelve to sixteen. The Great auk {Alca impennis) is 

 said to have possessed eighteen. 



The oil gland has often many apertures ; there are only 

 two in Brachyrhamphus marmoratus, but four in Lunda 

 cirrhata, six in Synthliborhamphus antiquus, and eight in 

 Uria columha.'' 



The skull is schizorhinal ^ and sohizognathous, with well- 

 marked occipital fontanelles * and impressions for supra-orbital 

 glands ; the latter nearly meet in the middle line, leaving but 



' Synthliborhamphus antigVMS has only one (the left). 



^ The remarkable shedding of the beak of the puffin (stated also to occur in 

 the penguin ; ef. P. Z. S. 1880, p. 2) has been described by Bueeau in Bull. 

 Sac'. Zool. Fr. ii. 1877, pp. 377, 432. See also ibid. iv. 1879, p. 1, for the same 

 phenomenon in other auks. 



' For osteology of auks see Owen, ' On Alca impennis,' Tr. Z. S. v. p. .317 ; 

 Shufeldt, /. Anat. Phys. vol. xxiii. ; and Pakkeb, ' On the Morphology of the 

 Duck Tribe (Anatids) and Auk Tribe (Alcidse),' Cunningham Memoirs R. Irish 

 Ac. No. 6, 1890. 



* These are sometimes obliterated with age. I find them present in a young 

 Uria troile, absent in an old one. In a specimen of Fratercula arctica there 

 was only one present. They also may be present or absent in Brachyrhamphus 

 and Synthliborhamphus. 



