PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL, 64, 



BRANTA MINUSCULA, new species. 



Characters. — Humerus similar to that of Branta canadensis (Lin- 

 naeus) but size small (smaller than in subspecies B. c, minima 

 Ridgway), angle of caput humeri at dorsal end of incisura capitis 

 abrupt, nearly a right angle, forming a distinct shoulder instead of 

 a gradual slope; head of humerus proportionately more narrow, 

 with external fossa relatively larger; external tubercle reduced. 



Descnption.—Type, Cat. No. 10548, U.S.N.M.. 

 proximal half of right humerus (figs. 3 and 4), col- 

 lected by J. W. Gidley, April, 1921, in quarry on 

 Sec. 22, T. 17 S., R. 20 E., 2 miles south of Benson, 

 Arizona. Upper Pliocene. 



Shaft (badly splintered but restored) with 

 slightly indicated sigmoid flexure; expanded 

 broadly to support humeral head, an acute ridge 

 extending to base of caput humeri at external mar- 

 gin on posterior face; deltoid ridge beginning on 

 side of bone well below lower margin of crista su- 

 perior, proceeding with a slight sigmoid flexure 

 inward toward center of shaft, with an abrupt con- 

 cavity beyond center of length where line is very 

 faint, terminating finally as an elongate tubercle set 

 at a slight angle external to median line of shaft, 

 separated by a space of 4 millimeters from the base 

 of the external tubercle ; ridge on end of shaft low 

 with sides meeting at a sharply pointed but obtuse 

 angle; the head of the humerus impressed below 

 caput humeri, this impression sharply delimited 

 proximally by a line continuous with the ridge on 

 shaft, and excavated slightly under lower margin 

 of caput humeri; tuberculum externum heavy, ele- 

 vated, external margin slightly curved, set with 

 outer margin not projecting later all}^ beyond ex- 

 ternal line of shaft ; tubercle excavated on posterior 

 face; external side straight, forming a right angle with pos- 

 terior face; proximal end projecting slightly bej^ond base of 

 caput humeri; caput humeri relatively low, with elongate, rounded 

 proximal surface, rounded in outline on anterior margin, angu- 

 lated posteriorly toward incisura capitis, with whole posterior 

 margin forming an overhang especially prominent toward incisura 

 capitis; inferior tubercle with point missing; incisura capitis deep, 

 narrow, ending as a simple notch on anterior face, but curving ex- 

 ternally on posterior side, where it is overhung by internal angle of 

 caput humeri ; fossa subtrochanterica moderately large, with a slight 

 shelf marking lower margin of crista inferior above which there is 



Fig. 3. — Proximal 

 pobtion of hd- 

 MEKUs (Type) of 

 Branta mincs- 

 ccla, posterior 

 VIEW. ( Nat. 



SIZE.) 



