ane 
Cope.) 620 [March 16, 1872. 
very large olfactory lobesin front. Cerebellum very small and flat ; middle 
brain large. This character is sustained by that of the ankle joint, which, 
existing in two such distinct divisions as the Amblypoda and Creodonta, 
may be found to characterize the entire sub-class, but this is not yet cer- 
tain; it 1s as follows: ‘Tibio-astragalar articulation flat, and without 
groove or segment of pulley. 
This sub-class stands below the Lyenccphala in its position, approximat- 
ing the reptiles in the points above mentioned, more nearly than the latter 
do. It includes two orders, one ungulate, the Amblypoda, the other 
unguiculate, the Bunotheria.* To the former belong the sub-orders 
Pantodonta and Dinocerata ; to the latter the Creodonta and probably the 
Tillodontu and Teniodonta. Whether the Mesodonta belong to it is not 
certainly ascertained, while the Insectivora do not belong to it, as they are 
rightly placed in the sub class Lissencephala. 
Lartct first pointed out the fact of the successive increase in the size of 
the brain of the Mammalia with the advance of Geologic time; and 
Marsh has stated that this increase is to be observed principally in the rel- 
ative size of the cerebral hemispheres. I would correct the latter state- 
ment so far as to add, that the increase of size is to be seen in the 
cerebellum as much as in the hemisphere. It is also evident that 
the relative decrease is in the middle-brain and olfactory lobes. 
Explanation of Plates. 
Pl. I. Cast of brain cavity of Coryphodon elephantopus, two-thirds the 
natural size. The right bulbus of the olfactory lobe is probably too large 
above, owing to the want of preservation of the superior wall of the cavity. 
Fig. 1. Superior view ; fig. 2, the left side; t. base of the trigeminus 
nerve. 
Pl. II. The same. Fig. 1, from below ; fig. 2, posterior; fig. 3, anterior 
views. t. base of the trigeminus nerve; md. base of the mandibular 
pranch of the trigeminus ; p, ribs continuous with anterior pyramids. 
* See Proveedings Academy Natural Sciences of Philadelphia, 1876, p. 88. 
PusiisHep APRIL 257TH, 1877. 
