136 ROY L. MOODIE 
or changed into a variety of mineral substances, such as kaolin,’ 
or phosphate (Eastman, ’08); or the form of the part may be 
retained by a cast of the cavity (Scott, 98), which the organ 
occupied. The latter is the manner of formation of the specimens 
of reptilian and mammalian brains described in the papers listed 
in the appended bibliography. 
The study of the brain cast of a mammal would give a more 
accurate idea of the anatomy of this organ than would the cast 
of the brain cavity of a reptile, since the brain in mammals more 
nearly fills the brain case (Osborn, 12) than it does in reptiles,‘ 
as noted by Dendy in the brain of Sphenodon. The cast in 
either case is of the dural cavity and gives only an approximate 
picture of the actual configuration of the brain of the animal, 
whether reptile or mammal, since the smaller convolutions 
make no impression of the inner surface of the skull (Scott, 
98, p. 874), even in man. If the brain of man were known only 
from the cast of the fossil crania, the greatly convoluted nature 
of the cortex would never be suspected (Gregory, ’14, fig. 8). 
On this account a study of brain casts is attended with consider- 
able uncertainty with respect to the value of all the characters. 
This has been overcome to some extent recently by Palmer 
(713) in his careful interpretations of brain structures of a fossil 
ungulate (Anoplotherium) from the Eocene of France. 
* The subject of Paleoneurology is still in its infancy. The 
earlier and pioneer publications dealt with the most obvious 
features of the specimens at hand, from which, to be sure, many. 
interesting and important generalizations were made. There 
is still much work to be done, however, from a strictly anatomical 
standpoint which will without doubt be of the greatest service 
in interpreting the relationships of the animals of the past. 
’ Moodie, Roy L. 1910. Amer. Nat’l., vol. 44, p. 367. Discusses the con- 
version of bone into kaolin and describes the preservation of a complete aliment- 
ary canal of a branchiosaur from the Coal Measures. 
4Dendy, A. 1911. Phil. Trans. Roy. Soc. Lond., Ser. B, vol. 201, pp. 227- 
ool, 
