880 THE WHITE RIVER FAUNA. 



M. 



Diameter of neck Of ilium J ''°*«^°P''«*''"°' ^^^ 



i exterointemal U0J5 



LoDg diameter of acetabulum 0045 



Anteroposterior diameter of ischium below Bpine OOJO 



Width of femur at proximal extremity 0090 



Diameter of head I a"*''^"P°«t''»°^ 2]^. 



( transverse 0U4o 



Transverse diameter at little trochanter 0065 



Transverse diameter at third trochanter 0060 



Transverse diameter at middle of shaft 0040 



Transverse diameter at condyles 0070 



Anteroposterior diameter at patellar ridge and condyles posteriorly 0080 



Diameter of head of tibia 5 ^°*«™P°^**"'''- °^^? 



( transverse moo 



Diameter of shaft of tibia transversely 0030 



Diameter distal end of tibia ^'"^*«'-''P°«**''°^ JJ^?^ 



c transverse 0065 



Length of astragalus 0070 



Length of trochlea 0035 



"Width of trochlea 0035 



„, ,. ^. ., ( externallv - 0632 



Elevation of trochlea < , • „ , 



I internally 0025 



_. ^ „, 1 Uong 0030 



Diameter of head < , " 



< short 0022 



Length of calcaneum 0010 



Length of heel of calcanenm 0045 



Width at tibial facet 0045 



Width at cuboid facet (transverse) 0035 



Depth at cuboid facet 00;?2 



It is very probable that this species is the progenitor of the Lepus syl- 

 vaticus, which now inhabits North America in such abundance. It will 

 then be interesting to trace the specific characters in which modification 

 was necessary in order to effect the transition. Only the principal ones 

 will be noticed; the few generic characters have already been pointed out. 



In the recent species the muzzle is similar in size; the premaxillary 

 bones are more produced on the extremity. The perforations of the ante- 

 rior part of the maxillary bone are larger and cover a greater extent of 

 surface than in the Palosologus liaydeni. The posterior emargination of the 

 palate is wider and deeper in Lepus sylvaticus. The otic bulla is a little 

 larger in P. haydeni, and the mastoid bone is not spongy with perforations 

 as in L. sylvaticus. Other parts of the skull cannot now be compared. The 

 preserved portions of the mandibular rami of P. haydeni are of the same 

 size as those of L. sylvaticus. The symphysis is shorter through the brevity 

 of the inferior portion of the sutural sui-face in P. haydeni. The incisive 



