Professor Marsh’s Monograph of the Dinocerata. 193 
“The results of this investigation were embodied by the 
author in a general law of brain-growth in the extinct mam- 
etn Partin time. This law, briefly stated, was 
PLTRE 21.—Skull of Hlotherium crasmum, Marsh. Mioce 
URE 28. --Skull of Platygonus compressus, LeConte. Piseak. 
l. All Terti mammals had small brains. 
Ss oe es gradual increase in the size of the brain dur- 
- This Sisko was confined oe to the cerebral hemi- 
*Pheres, or higher portion of the ca 
i, 22 some groups, the convolntions ‘of the brain have grad- 
ually one more comple 
: me, the cerebeltlin and the olfactory lobes have 
even aint in size. 
8 some evidence that the same Spode law of brain 
ity Ab wth old on, for Birds and Reptiles from the Cretaceous 
Pi 5 Si July, 1874; and vol. xii, p. 61, July, 1876; also 
oi er vs va, p. 66, July, 
