LAGOMOEPHA. 873 



of the bone, and its extremity is a facet for contact with the calcaneum. 

 On its external face is a prominent process directed backwards. The ex- 

 ternal trochlear groove is deeper than the internal, and is well separated 

 from it. The internal malleolus can scarcely be said to exist. It may be 

 represented by a small process on the inner side of the extremity of the 

 shaft. 



The astragalus is elongate and flat, and the trochlear portion is oblique. 

 The neck is elongate, and convex on the inner side ; the constriction is on 

 the inner side immediately behind the head. The long diameter of the 

 latter makes an angle of 45° with the horizontal plane. The external troch- 

 lear arc is much larger than the internal. The cotylus, which fits the ex- 

 ternal condyle of the calcaneum, possesses a peculiar impressed area on its 

 posterior surface. The calcaneum extends nearly as far anterior to its con- 

 dyle as posterior. The free portion is subcylindric or subquadrate to the 

 end. The internal process for the astragalus is quite jjrominent. The cuboid 

 facet is directed obliquely inwards, running into a short longitudinal groove. 

 The cuboid extremity is little depressed. 



The skeletal characters above enumerated were taken from the bones 

 of P. turgidus and P. liaydeni, excepting in the cases of the ulna, radius, ilium, 

 and calcaneum, which were derived from those of P. haydeni only. 



A cast of the cranial chamber of a specimen of Palceolagus haydeni dis- 

 plays the superficial characters of the brain. As in the order generally, the 

 hemispheres are small and are contracted anteriorly. The greater part of 

 the cast of the cerebellum is lost, but enough remains to show that it was 

 large. The olfactory lobes are large ; they are not gradually contracted to 

 the hemispheres, but expand abruptly in front of them, being separated by 

 a constriction only. They are wider than long, and than the anterior ex- 

 tremity of the hemispheres. Their cribriform surface is wide, and extends 

 backwards on the outer sides. Traces of the three longitudinal convolu- 

 tions can be observed on the hemispheres above the lobus hippocampi. The 

 internal and median are continuous at both extremities, and with the exter- 

 nal to the base of the olfactory lobes. There is no definite indication of the 

 Sylvian fissure. The lohus hippocampi protrudes laterally a little beyond the 

 border of the external convolution. Its form is depressed. 



