104 CARINAT^. 



proximal articular surface. The femur i« comparatively long and 

 straight. 



The distal expansion of the coracoid is but slight, the sternal 

 articulation does not extend far up on the inner surface, and in the 

 type genus the inner sternal angle is much inflected. The humerus 

 is comparatively short, and in the type geuiis is small and much 

 compressed laterally. 



The compression of the beak is generally strongly marked — most 

 so in the type genus. 



Genus ALCA, Linn. ' 



Tiie type genus. The beak is straight, large, much compressed, 

 and strongly deflected towards the extremity. 



Alca impennis, Linn. ^ 



The largest species. The wings are aborted and useless for flight. 

 Hah. Northern Europe and America. 



A. 152. The imperfect skeleton ; from a Guano deposit at Funk 

 Island, off Newfoundland. Nearly all the bones with the 

 exception of the phalanges are present, but all of them do 

 not belong to one individual. Ftuxhased, 1875. 



Suborder XVIII. IMPENNES. 



This group is sufliciently distinguished by the structure of the 

 tarso-metatarsus (fig. 44), which is very short and wide, with the 

 three metatarsals only united by thin plates of bone, and vacuities 

 between them below the tarsus. The tibio-tarsus is moderately 

 long, with the cnemial crest extending far down on the shaft, the 

 distal extremity inclined inwardly, no intercondylar tubercle on the 

 extensor bridge, and the proximal extremity of the entocondyle free 

 and hook-like ^ The coracoid is long, narrow, and gradually 

 widening distaUy ; the distal part is very concave on the dorsal and 

 convex on the ventral surface ; and the proximal part of the dorsal 

 surface is flattened ; there is no hyosternal process, the postcro- 

 sternal angle being truncated ; and the subclavicidar process is very 



1 Syst. Nat. ed. 12, vol. i. p. 210 (1766). - Loc. eit. 



^ This character, together witli tlie more proniiuent extensor bridge, at ouee 

 distinguishes the tibio-tarsiis of the Impennea from that of the Auseres. 



