1910.] Carpus <>/ insaiivurcs, Rodents, Tilludunts, Crcudunts. 445 



lunar-unt'it'orin contact becomes broad. In Blarinn, on tlic confrarv, in 

 which the nianus is very slender the carpals are flatter and the Innar-nnci- 

 form contact sli<>ht. In Tupaia, which retains many i)riniitive characters 

 throughout the skeleton, the centrale remains free, the limar-unciforni 

 contact is of moderate size, and the pollex is ])artly divergent. TIk^ scaphoid 

 however, is fused with the lunar. In the terrestrial Rhi/uchocyou, as figured 

 by Peters (1852, pi. xxiii, fig. 2), digit I is lacking, the carpals are flattened 

 and the lunar-unciform contact (at least in front view) is very slight. In 

 the allied Petrodromus (/. c, pi. xxiii, fig. 6) digit I is reduced, the magnum is 

 relatively large and separates the lunar from the unciform, but in the back 

 view (/. c, fig. 6a) the lunar-imciform contact appears to be well developed. 



The ancestral Insectivores certainly had a free centrale. If they were 

 arboreal or semi-arboreal forms with more or less spreading feet as sug- 

 gested above (p. 288), then they very likely had at least some contact between 

 the lunar and the unciform. 



Rodentia. The carpus in forms with spreading digits {c. cj., Fiber, CV/.v/o/') 

 has oblique carpal facets and a broad hmar-unciform contact. In the 

 forms with narrow feet of ambulatory type {e. g., Mii.'i, Lepus) the carpals 

 are broad and flat and the lunar-unciform contact is small. The centrale is 

 usually free liut the scaphoid is often fused with the lunar. In Mas the 

 front view of the centrale shows it as a very small round bone, but dissection 

 of the carpus shows that the centrale is really broad and much flattened. 



Tillodontia. The details of the carpus of the Lower Eocene E-sthonyx 

 acutidens are very suggestive of the Creodont tyi)e. The trapezium is large, 

 the scaphoid shallow, the centrale occupies the same position as it does in 

 Creodonts, the magnum is keeled on top, the unciform is high, and the cunei- 

 form is shallow. The lunar rests about equally on the centrale, magnum 

 and unciform. 



Creodonta. The manus of the Basal Eocene forms is partly known in 

 Dissacus carnifex (figured by Osborn and Earle, 1895, p. 33) a primitive 

 member of the Mesonychidiie; and in CAoenodon corrugatus (figured by 

 Matthew, 1901, p. 14), a member of the Arctocyonidfie. The manus is also 

 known in Dromocyon (Fig. 26, p. 405) and Mesonyx, in Hycenodon, Sinopa, 

 Oxywna, Patriofelis and others. The })rimitive features of all these forms 

 may conveniently be summarized in the accompanying generalized scheme 

 of the Basal Eocene Creodont manus (Fig. 29). The most noteworthy 

 features are the large trapezium and divergent pollex, the large free centrale, 

 small trapezoid, magnum smaller than lunar, lunar resting almost equally 

 on centrale, magnum, and unciform. In regard to the digits, D. I is diver- 

 gent, D. II overlaps III and III overlaps IV. This overla})ping was formerly 

 regarded as an evidence of marked "displacement" but it is much more 



