LAGOMOEPHA. 885 



trochanter is smaller, and its apex is the end of the truncate external sur- 

 face of the great trochanter. In P. haydeni the two are connected by a 

 thin edge. 



The great trochanter projects considerably beyond the head, and the 

 little trochanter is very prominent, and is directed posteriorly. The condyles 

 of the femur are not produced so far backwards as in P. haydeni. In all 

 the particulars which I have described as characterizing the distal extremity 

 of the tibia of P. haydeni, P. turgidus agrees with it, differing only in size. 

 The same may be said of the astragalus, excepting that the inner trochlear 

 ridge is a little less reduced in the P. turgidus. 



Measurements. 



II. 



Diameter of distal end of humerus^ anteroposterior, least 004 



t transverse 012 



"Width of proximal end of femur 013 



Diameter of head ^'*°*''""P''»t''"°'" ^ 



( transverse .0065 



Width of femur at little trochanter 008 



Width of femur at third trochanter 007 



Width of femur below third trochanter 005 



Width of condyles of femur 010 



Depth of same at posterior margin 010 



Diameter of shaft of tibial ''"t'^^P''^*''""'^ ^^* 



i t ranaverse 005 



Diameter of distal end of tibia ^ ' vvMt 



< transverse 0110 



Length of astragalus 0110 



Length of trochlea 0056 



Width of trochlea 0060 



Elevation l"f«*''"^^l"'^g« O^^^ 



( of internal ridge 0040 



Diameter of head P°°g "O^O 



( short 0033 



White River beds of Dakota, and of Northeast Colorado. 



LEPUS Linn. 



10 ^ ^ 



Dental formula: I. :r ; C. - ; Pm. - ; M. -. First superior molar sim- 

 1 (J 2 n 



,ple; first inferior molar with two external grooves; last inferior molars 



consisting of two cylinders. Postorbital processes present. 



I am acquainted with but one extinct species of this genus, and this 



is from the John Day or Middle Miocene period. It proves the ancient origin 



