ART. 5. 



FOSSIL BIRDS FROM ARIZONA WETMORE. 



a slight elevation serving as a raised threshold for the main fossa; 

 opening of fossa rudely ovate with internal pneumatic foramina; 

 projecting angle of crista superior missing; base showing impressed 

 curved line of muscle attachment; bicipital surface broad, regularly 

 rounded, delimited posteriorly by a curving, faintly impressed, but 

 distinct bicipital groove; crista inferior with rounded outer margin 

 forming a clean cut angle at junction with shaft; deltoid groove 

 broad, shallow, poorly marked; coraco-humeral 

 groove broad, shallow, indistinctlj^ delimited until 

 it reaches level of incisura capitis, where it becomes 

 suddenly narrowed with elevated margins, and ter- 

 minates as a deep cleft, with walls meeting at bottom 

 in an acute angle on lower margin of inferior tu- 

 bercle, the external end of groove open without im- 

 pression ; a slight overhang of proximal wall beyond 

 incisura capitis ; a slight excavation between tuber- 

 €ulum externum and base of caput humeri. 



Measurements in millimeters. — Transverse diam- 

 eter of shaft below crista superior 9; width of 

 head from external point of bicipital surface to line 

 of external margin of tuberculum externum 21.7 

 (projecting points of bone broken away in such a 

 manner as to make taking of definite measurements 

 difficult). 



ReyiuLrks. — This bird is remarkable cliiefl}^ for its 

 size, as it seems from the fragment available to rep- 

 resent a form smaller than the smallest li"vdng 

 representatives of Branta canadensis. It is a mem- 

 ber of the group containing the Canada goose and 

 is not a sea goose or brant {Branta hernicla group) 

 as these differ from canadensis in that they lack 

 the impressed space on the head of the shaft below 

 the caput humeri, a character in which brant re- 

 semble Chen and A7iser. Branta minuscula would seem to have been 

 but a trifle larger than our large ducks. 



Family ANATIDAE (indeterminate). 



Three fragmentary coracoids represent as many species of duck- 

 like birds that may not be identified with certainty. The largest of 

 these three, a nearly complete coracoid, represents a bird about as 

 large as a canvasback, and may have been a member of the subfamily 

 Anserinae. The two others seem to belong in the subfamily Fuligu- 

 linae, and appear to have come from birds somewhat smaller in body 

 than the lesser scaup or harlequin ducks. All three specimens come 

 from the quarry 2 miles south of Benson. 



Fig. 4. — Proximal 

 portion op hu- 

 MERUS (Type) of 

 Branta minus- 

 cula,. ANTERIOR 

 VIEW. (Nat. 



SIZE.) 



