980 ME. w. 5. PTCBA5T ON THE [Dee. 13, 



ill other geuera the base of the triangle greatly exceeds the height 

 from base to apex. Eudyptida is easily distinguishable from the 

 remaining genera on account of its small size ; the ulna does not 

 exceed 2 in. in length — the whole wing is under 5 in. 



The most striking feature of the wing is the remarkable 

 compression or flattening, dorso-yentrally, which the bones have 

 undergone. The sub-trochanteric (pneumatic) fossa of the 

 humerus is of great size, as in many Anatidae ; in the Penguins, 

 however, the fossa is non-pneumatic. The pectoral crest does not 

 project beyond the level of the shaft; the pectoralis major is 

 inserted into a deep oblong fossa on its ventral aspect. The 

 coraco-humeral groove is well-marked. The head of the humerus 

 is reniform, the hilus being ventral. The distal articular end is 

 obliquely truncate ; the radial and ulnar condyles lie one behind 

 the other, and from behind the latter the shaft is produced into a 

 sharp angle, the free border of which is grooved; there is a 

 second groove dorsad of this perfected by a large projecting upper 

 lip. In these two grooves run two sesamoids, the form and relations 

 of which have been frequently described. 



In a half-grown nestling of G. chri/socome the 1st metacarpal is 

 quite separate from the 2nd and tipped with cartilage — representing 

 the 1st phalanx. The terminal phalanges of the 2nd and 3rd 

 metacarpals are likewise tipped with cartilage, and similarly may 

 represent phalanges. The ulnare at this stage is entirely carti- 



laginous. 



viii. The Peltic Limb. 



The most characteristic feature of the pelvic limb is the 

 distinctness of the three metatarsals, usually merged together into 

 a longer or shorter single cylindrical shaft. In the Penguins 3 

 metatarsals are always distinguishable, separated one from another 

 by grooves more or less deep. On either side of the 3rd meta- 

 tarsal, on anterior view, lie 2 foramina ; just below the insertion for 

 the tibialis anticus these pass through to appear just below the bases 

 of the two more or less distinct calcaneal ridges. The form of the 

 tarso-metatarsus in the Impennes is closely approached by that of 

 Fregata (a Steganopodous bird) ; but it can easily be distinguished 

 therefrom by the fact that in Fregata the 2nd trochlea is longer 

 than the 3rd and is directed backwards, and by the presence of 

 a foramen at the distal end betw een the 3rd and 4th trochleae. 

 In Sphenisd this foramen is wanting, and the 2nd trochlea is 

 shorter than the 3rd and is not directed backwards. It has been 

 suggested that this distinctness of the metatarsals in the Impennes 

 is pseudo-primitive and probably induced by the plantigrade habit 

 of walking. The Penguins are, however, not plantigrade ; and it is 

 a significant fact that both in this group and in Fregata the legs 

 are comparatively little used for the support of the body. Thus 

 it is possible that on this account the metapodial region may have 

 retained a nearer approach to the primitive condition than in 

 other forms. They represent a halfway stage between the 



