A FOSSIL 0\VL FROM WYOMING WETMORE 29' 



jecting strongly distaily, and set at a distinct angle with the central 

 axis of the shaft (a portion of the posterior projection missing) ; 

 considerably compressed from side to side, with free margin nar- 

 rowed; middle trochlea relatively broad and heavy, separated from 

 the external trochlea by a narrow, shallow sulcus; anterior surface 

 merging smoothly with lower end of shaft; articular surface deeply 

 marked on posterior face by a sharply angular groove, the outer 

 margin bounding this groove projecting farther than the inner; 

 axis of trochlea making an oblique angle toward the outside with 

 the axis of the shaft; internal trochlea relatively heavy, projecting 

 rather abruptly beyond the free margin of the shaft; anterior face 

 with a broad, smooth articular surface, and posterior face deeply 

 grooved (outer, free margin missing) ; outer face with a deep, some- 

 what irregular pit; separated from the middle trochlea by a shallow, 

 narrow groove; lower end of shaft broad, roundly concave on the 

 anterior face, and broadly grooved behind; a well-marked inferior 



Figure 5. — Protostrix mimlca, new species : Distal end of metatarsus. Natural size. 



foramen. Bone dull dark brownish gray in color, well fossilized. 

 Transverse breadth across trochlea 13.2 mm (other pertinent meas- 

 urements not available). 



Compared with living Strix varia of the family Strigidae the 

 fossil has the outer trochlea much broader when viewed from the 

 side, the anterior base of the middle trochlea merging smoothly 

 with the base of the shaft instead of projecting abruptly, and the 

 internal trochlea relatively smaller when viewed from in front. It 

 is nearer to the Strigidae in its characters than to the Tytonidae 

 and is sufficiently different to support the separation of Protostrix 

 in a distinct family. It will be recalled that to this time the Proto- 

 strigidae have been separated on the basis of characters found in 

 the distal end of the tibiotarsus. 



Discovery of this new species increases the number now known 

 in the Protostrigidae to four, as follows: Protostrix lyddeheri (Shu- 

 feldt), P. leptosteus (Marsh), ^ P. saurodosis (Wetmore), and P. 

 mimica Wetmore. 



Drawings of the specimens described herein were made for me b,y 

 Sydney Prentice. 



2 For reference of Buho leptosteus Marsh to this genus, see Wetmore, Condor, 1937, 

 pp. 84-85. 



U. S. GOVERNMENT PRINTING OFFICE: 1937 



