F. B. Loomis — The Genus Stenomylus. 297 



Art. XXIY. — Osteology and Affinities of the Genus Stenomy- 

 lus • by Frederic B. Loomis. 



During the summer of 1907 tlie Amherst College field party 

 while prospecting in. the sandstones of the Lower Harrison 

 levels some five miles to the southeast of the Agate Spring 

 postoffice, Sioux Co., Nebraska, found fragments of a Steno- 

 mylus smaller than the S. gracilis then known. During that 

 season a few badly shattered remains were collected, after 

 which work was continued in other sections of the field. On 

 returning the next season, however, the same levels were fur- 

 ther excavated, on which it developed that there was a verita- 

 ble quarry of these skeletons at this locality ; for no less than 

 eighteen skulls, together with enough disarticulated bones to 

 represent the complete skeletons, were collected from one 

 pocket, and in an adjacent portion of the hill three complete 

 skeletons were found. Following this the Yale University 

 party collected three skeletons, the American Museum party 

 five or six skeletons, and the Carnegie Museum party five or 

 six. During the season of 1909 the Carnegie Museum again 

 collected in this quarry, obtaining a large number of skeletons. 

 Thus already not less than forty skeletons, and I should esti- 

 mate many more, have been taken out, and as the specimens 

 are found along over 150 feet of the face of the hill, I see no 

 reason why as many more complete skeletons should not be 

 obtained from the same source. With this wonderful and 

 well-distributed material there is every reason that a complete 

 description should be made both for identification, osteological 

 study, and comparison. 



The quarry. — The Stenomylus quarry is located some five 

 miles due southeast of Agate Spring postoffice, and about one 

 and a half miles up the " draw " south of the upper Harris 

 place, and about the same distance a little east of south from 

 the famous Agate Springs quarry of the Carnegie Museum. 

 The horizon is in the Lower Harrison beds about 75 feet from 

 their upper boundary. The matrix is a fine, homogeneous, 

 well-bedded, soft sandstone, which differs materially from the 

 much coarser and more irregularly bedded sandstone typical of 

 these beds. These fine sands are about 100 feet in thickness 

 and seem to have a limited extension, being traced only about 

 three-fourths of a mile to the south and thinning out very soon 

 in the other directions. To the east the Upper Harrison beds 

 directly overlie these fine sandstones. The Stenomylus remains 

 occur in two levels ; the one about four feet above the other, 

 and both some 70 feet below the top. In the lower of the two 



