Fig. 1 Dorsai view of the endocranial cast of a primitive rodent, possibly 
a sciuromorph. The cast displaces 2 cc. of water. White River Oligocene of 
South Dakota. No. 629 Walker Museum, University of Chicago. The sub- 
divisions of the brain are perfectly obvious. The entire length of the cast is 
24 mm. 
Fig. 2 Right lateral view of the same cast. 
Fig. 3 Dorsal view of the endocranial cast of a primitive saber-toothed cat, 
Dinictis felina Leidy. White River Oligocene of South Dakota. The cast 
displaces 52 cc. of water. Field Museum. The entire length of the cast as 
figured is 80 mm, 
Vig. 4 Right lateral view of same cast. 
Fig. 5 Dorsal view of endocranial cast of a primitive insectivore, Ictops 
acutidens, of the family Leptictidae. The cast displaces 5 ec. of water. No. 
622, Walker Museum, University of Chicago. White River Oligocene. Length 
of entire cast, 27 mm. 
Fig.6 Right lateral view of same cast. 
Fig. 7 and8 Dorsal and right lateral views of same genus, possibly. the 
same species. No. 628, Walker Museum, University of Chicago. Since this 
cast displaces only 4 ec. of water, it is smaller than the cast in figures 5 and 6. 
Length of entire cast, 28 mm. 
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