40 



THE AMERICAX XA TrRAlJST. [X , .1. XXXV 1 1 1. 



lengths of these two metacarpals is anythini; like it. The prox- 

 imal phalanx of the pollex is also long and compressed. It 

 bears a claw upon its extremity. Both of the other metacarpals 

 are long and very straight, allowing but a narrow interval to 

 exist between them. 



The blade of the proximal phalanx of the index is meagre, 

 being fiat anconad and faintly pitted upon the opposite side- 

 Its distal joint also bears a claw. 



The phalanx of the middle finger is fully half as long as the 

 expanded one of index alongside of which it lies. 



These observations upon the pectoral limit of the Urinatoridae 

 have been jotted down during my examination of this part of 

 the skeleton in a specimen of ['. Invinic, and in it I find the 

 skeleton of the manus, just described, equalling in length the 

 bones of the antibrachium. 



The humerus in this diver has a length of about 14.5 cm. ; 

 the radius 1 1 .4 ; the ulna 11.65; manus 11.8, of which latter 

 the carpo-metacarpus claims 7.5 cm. From this it is seen 

 that when the skeleton of the limb is in a position of rest 

 and closed alongside the chest, the humerus projects beyond the 

 bones of the anti-brachium for some little distance. This is not 

 the case among the Laridae, whereas it agrees with Aka tarda, 

 Uria, and, I expect, the Alcidae generally. 



The Pelvic Limb jn the Urinatorid.^^:. 



The skeleton of the pelvic limb in the Urinatoridje is a very 

 interesting structure, and highly characteristic of the family. 



Coues has described its mechanism and structure in U. imbcr 

 in his memoir before alluded to, and I will here record a few 

 observations that I have made upon this limb as found in 

 Urinator Inmnie. 



The femur is short and thick, being about as long as the 

 cnemial process of the tibio-tarsus above the articulation. Its 

 short shaft is somewhat cylindrical near the middle, bowed to 

 the front, and scarred in many places by tuberous projections 

 for muscular insertion. The head is large and globular, sessile, 

 and deeply marked by the pit for the ligamentum teres. Dis- 



