t'opc] v)l. J [March 16, 1877. 



very large olfactorv lobes in front. C'crebelluni very small and flat ; middle 

 brain large. Tliis eliaracter is sustained by that of the ankle joint, which, 

 existing in two such distinct divisions as the Ambljipoihi and Cre»donta, 

 may bo found to characterize tlu; entire sub-class, but this is not yet cer- 

 tain ; it IS as follows : Tibio-astragalar articulation tial, and without 

 groove or segment of pulley. 



This sub cla-ss stands below the Lyenaphdla in its position, appro.ximat- 

 ing the rejjtiles in the points above mentioned, more nearly than the latter 

 do. It includes two ordere, one ungulate, the Amhlypoda, the other 

 unguiculate, the Bunoikeria.* To the former belong the sub-orders 

 Paiitdilonta and Dinocerata ; to the latter the Cveodonta and probably the 

 Tillodontd and Twniodonta. AVhether the Mestodonta belong to it is not 

 certainly ascertained, while the Imectivora do not belong to it, as they are 

 rightly placed in the sub class Lissencephala. 



Lartet first pointed out the fact of the successive increase in the size of 

 the brain of the Manvmdia with the advance of Geologic time ; and 

 Mai-sh has stated that this increase is to be observed principally in the rel- 

 ative size of the cerebnil 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 olfactorv lobes. 



ExjilaiKition of Phitm. 



PI. I. Cast of brain cavity of Coryphodon elephnntoput, two-thirds the 

 natural size. The right bulbus of the olfactory lobe is probablj' too large 

 above, owing to the want of preservation of the superior wall of the cavity. 



Fig. 1. Superior view ; fig. 3, the left side ; t. base of the trigeminus 

 nerve. 



PI. II. The same. Fig. 1, from below ; fig. 2, posterior ; fig. <», anterior 

 views, t. base of the trigenunus nerve : md. ba.se of the mandibular 

 branch of the trigeminus ; p, ribs continuous with anterior pyramids. 



■ !Sce I'rocef'diiiiis AciKlcin.v N'ntiiral Sciences of Pliiliulcl|ilii:i, IsTH, (>. ss. 



