18b8. ] PROCEEDINGS OP UNITED STATES NATIONAL MUSEUM. 259 



common to birds; its head is rather broad and compressed from above 

 downward. 



The entire pectoral arch is non-pneumatic, in keeping with the most 

 of the rest of the skeleton. 



The body of the sternum in Oceanodroma is of a square outline, with 

 its postero-lateral angles slightly produced and its xiphoidal border en- 

 tire. Above it is concave, being correspondingly convex upon its pec- 

 toral aspect. The carina is deep in front and gradually slopes to the 

 mid-point of the hinder border of the sternal body. Its angle protrudes 

 and its anterior margin is concave. 



Each costal border has six articular facets upon it, and the costal 

 processes are triangular in outline and quite prominent. The manu- 

 brium is wedge-shaped and small, and the coracoidal grooves nearly or 

 quite meet at its base. 



The chief pectoral muscular line starts from a point on the lower lip 

 of a coracoidal groove half way between the manubrium and costal 

 border, to be produced posteriorly and terminate at the junction of 

 hinder and middle thirds of the line made by the carina where it joins 

 the sternal body. This bone is non-pneumatic. 



Of the appendicular skeleton. — When closed in a position of rest the 

 bones of the antibrachium rather exceed in length the humerus, and 

 both are long for the size of the bird. 



The shaft of the latter bone is subcylindrical and nearly straight, 

 viewed from any aspect. Curling, as it does, far over the pseudo-pneu- 

 matic fossa, the ulnar crest forms a prominent feature at the proximal 

 end of the bone. Another and smaller fossa, protected somewhat in a 

 similar manner by the overhanging humeral head, is separated from 

 the former by a bony bridge. 



The radial crest is short, but well pronounced, with its free border 

 convex. 



At the distal extremity of the humerus we notice a conspicuous ecto- 

 condyloid process, and to its inner side at the base of the shaft, beyond 

 the trochlear tubercles, a deep pit. 



The auconal aspect of this extremity is profoundly marked by a me- 

 dian tendiual groove. The bone is about 3.5 centimeters long. 



After very careful search at the elbows of all four of these specimens 

 of Oceanodroma furcata I fail to find the slightest trace of anything like 

 a sesamoid bone, and the specimens are in a condition, too, that if they 

 existed they would more than likely be there. 



I am aware of the existence of Eeinhardt's paper upon this subject, 

 but it is not at the present writing available to me, and I can not say 

 whether he claims to have found these sesamoids in Oceanodroma or not. 



The shaft of radius is very straight and that of the ulna not much 

 bowed, so we have a small interosseous space in this Petrel. 



The skeleton of manus is long (4.5 cm ), but does not call for special re- 

 mark beyond the fact that pollex digit does not bear a claw, nor does 



