REPORT ON THE SPHENISCID^. 



33 



metacarpus, with both of which bones it articulates. Both the articuLar surfaces of the 

 bone are concave, that for the reception of the extremity of the radius being deeper than 

 that which articulates with the metacarpus. 



The idnar carpal hone (PL VI. figs. 13, 14, 15) is of much larger size than the 

 radial. It presents in Eudyptes chrysocome the form of an isosceles triangle, the apex of 

 which is directed downwards. The upper and external angle of the figure is somewhat 

 prolonged to form a projecting tubercle provided with two articular surfaces. The upper 

 of these is concave and articulates with the distal end of the ulna, while the lower, irreo-ular 

 in form, articulates with the proximal extremity of the metacarpal bone. The internal 

 surface of the bone is flat, the external slightly hollowed from above downwards. The 

 anterior and posterior borders of the bone are of equal length, and slightly exceed that of 

 the superior border, which is directed upwards. 



The radial carj)al bone presents the same form in every species of Penguin. The 

 ulnar carpal is similar in form in Eudyptes, Aptenodytes, and Spheniscus. In Pygosceles 

 the length of the bone relatively to its breadth is greater than in any of the other genera. 



It is impossible to give measurements of the radial carpal bone. Those of the ulnar 

 carpal are subjoined in inches. 



Species. 



Eudyptes chrysocome, from Tristan, 



Eudyjjtes chrysocome, from the Falklands, 



Eudyptes chrysocome, from Kerguelen, 



Eudyptes chrysolophus, 



Spheniscus demei-sus, . 



Spheniscus magellanieus, 



Spheniscus mendiculus, 



Spheniscus minor, 



Pygosceles tceniatus, . 



Aptenodytes longirostris, 



Length of radial 



bonier of ulnar 



carpal bone. 



Length of ulnar 



border of ulnar 



car])al bone. 



Length of upper 



border of uluar 



carpal bone. 





The Metacarpus. 

 The metacarpus of the Penguins consists of a single bone, which, however, clearly 

 shows its originally compound character even in the adult. The elements of which 

 it is composed are three in number. The first or radial metacarpal bone is of 



(ZOOL. CHALL. EXP. — PART XVIII. — 1883.) 



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