14 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.64, 



ing no sinuation ; middle trochlea with inner and outer margins nearly 

 parallel, very slightly convergent at upper end on posterior face; 

 outer trochlea sejDarated from middle by relatively broader groove. 

 Description. — Type, Cat. No. 10549, U.S.N.M., distal end of right 

 tarso-metatarsus, (figs. 8 and 9) collected by J. W. Gidley, March, 

 1921, in quarry 14 miles southeast of Benson, Ariz. Upper 

 Pliocene. Lower end of shaft slightly rounded anteriorly, though 

 broad and comparatively plane, expanded to support the distal troch- 

 leae; a distinct external groove that becomes deeper to terminate in 

 the inferior foramen, well above the external intertrochlear sulcus; 

 shaft expanded more toward outer than toward inner side ; external 

 trochlea compressed, with anterior external angle cut away in an 

 abrupt slope that forms an angled articular facet for fourth toe, 

 with a very faint central sulcus, and an equally slight basal excava- 

 tion to receive the end of the facet of basal digit of the outer toe ; ex- 

 ternal face of external trochlea flattened but slightly rounded (ex- 

 ternal posterior margin imperfect) ; external intertrochlear sulcus 

 moderately deep with rounded bottom and very slightly divergent 



sides, continued as a well-marked groove that 

 passes back to become continuous with the 

 groove containing the inferior foramen ; mid- 

 dle trochlea moderately strong, with sides 

 whose faces are excavated to form distinct 

 Figs. 8 and 9.-lower end j^g^jian concavities ; in laterial outline evenly 



OF TARSO-METATARSUS OF ' _ "^ 



chloroenas micula, an- rounded on free portion to form an ellipse 

 TERioR AND POSTERIOR ^^-^j^ postcrlor sidc sli^htly flattened; a 



VIEWS. (X 2.) i . 



rather broadly excavated median groove that 

 merges with the shaft posteriorly and on anterior face terminates in a 

 distinct pit; on the posterior side with external margin projecting far- 

 ther, and extending somewhat higher on shaft, than inner ; inner mar- 

 gin lower, converging slightly at upper end toward center of trochlea ; 

 internal digital trochlea, viewed from in front, broad, with surface 

 rounded ; internal face flat, projecting posteriorly well beyond middle 

 trochlea, and placed correspondingly less far forward on anterior 

 face, where the middle trochlea projects anterior to it; posterior 

 face with a sharp posterior projecting ridge, with a very slight sulcus 

 at its base; a distinct winglike inner tubercle or ala interna project- 

 ing as a rounded, somewhat flattened cone at a right angle from the 

 outer face of this posterior portion ; ala interna well separated from 

 main trochlea; posterior face of shaft slightly excavated in center, 

 forming a longitudinal trough with rather sharp margins. 



Measuremerits in millimeters. — Greatest breadth across trochlea 

 5.4 mm. ; transverse diameter of inner trochlea, including ala interna 

 2,0 mm.; transverse diameter of middle trochlea 1.5 mm.; transverse 

 diameter of external trochlea 1.2 mm. 



