FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 139 



is not SO accurately measurable but is recorded A\athin the range 1.0 

 to 1.3, mean 1.16, for these eight specimens. P4, poorly preserved 

 and very difficult to measure, has a maximum oblique diameter of 

 about 1 mm and a width of 0.6 or 0.7 mm. M2 is well preserved only 

 in the type of Megopterna minuta, where it is 1.4 mm in length and 

 about 1 mm in wddth. The less completely preserved specimens of 

 this tooth do not suggest a deviation of more than 0.1 mm from this. 

 The one Silberling Quarry specimen in the National Museum col- 

 lection has Ml with the dimensions 2.8 and 1.1, well within the range 

 of the Gidley Quarry material. 



Family Uncertain 

 Genus and species undetermined 



Figure 29 



U.S.N.M. no. 9777, from the Gidley Quarry, is a right humerus 

 of a fossorial mammal of about the size of a recent Scalops. It is 

 imperfect but preserves highly characteristic features. The laterally 

 compressed head, short, stout, twisted shaft, and flattened, widely 

 flaring distal end are disposed in such a way that if the head was 

 directed posteriorly, the entepicondyle was anterior and only very 

 slightly internal in position, and the ectepicondyle similarly posterior, 

 «o that the lower arm was throv/n outwards almost at right angles 

 to the body. The bicipital groove, mainly occupying the proximo- 

 internal quarter of the posterior face, is deep and narrow, bounded 

 by sharp crests and elevated tuberosities, which are, however, broken 

 off. The pectoralis major insertion is broad and shallow, occupying 

 most of the proximal half of the anterior face of the shaft, and not 

 sharply bounded distally. The deltoid process is broken, but from 

 its base it was more prominent and more internal than in Scalops, 

 more proximal and heavier than in Arctorydes. The notch between 

 head and ectepicondyle is nearly semicircular. The distal end has 

 greatly produced epicondyles, the extension of the ectepicondyle far 

 beyond the globular capitulum being especially striking, in comparison 

 with Scalops. The other distal articulations are poorly differentiated 

 or preserved. The entepicondylar foramen is strangely developed as 

 a long, small canal, running from the posterior face near the internal 

 margin to the middle of the anterior face of the broad distal end. 



This peculiar humerus resembles those of recent moles in many 

 respects but also differs throughout in detail. Unquestionably the 

 resemblance bespeaks similarity of habits. Whether it also indicates 

 phylogenetic affinity is quite uncertain. In some respects resemblance 

 is closer to Arctorydes from the Ohgocene (see Schlaikjer, 1933), but 

 there are also numerous differences: The distal end is more nearly 

 parallel to the long (anteroposterior) axis of the head; the deltoid 



