lyon] the hares and their allies 3^9 



presternum, its posterior extremity about as much expanded as its 

 anterior. These sterna are found in the genus Orycfolagits. (PI. 

 xcv, 5.) One skeleton of Oryctolagiis (No. 49,648) shows the 

 peculiarity of five segments in the mesosternum, the fifth being very 

 small and short. As in the case of tlie abnormal sternum of Lepns 

 tcxianus, No. 94,198, also with five mesosternal segments, only one 

 pair of ribs is attached to the junction of the fifth mesosternal seg- 

 ment with the xiphisternum. 



4. Presternum compressed with low keel all along ventral border, 

 dorsal portion somewdiat expanded just anterior to the attachment 

 of the first pair of ribs which takes place at the junction of the 

 anterior and middle thirds. j\Iesosternum of four distinct segments, 

 the first compressed laterally with a low keel continuing that of the 

 presternum, the succeeding mesosternal segments becoming suc- 

 cessively wider and more dorso-ventrally flattened. The last seg- 

 ment is much wider than any of the others, with a well-marked 

 postero-lateral angle for the attachment of the last two sternal ribs. 

 The xiphisternum is decidedly longer than the presternum ; it is 

 slender in the middle, but the ends are considerably expanded, espe- 

 cially the posterior end. This type of sternum is found in the genus 

 Bracliylagus. (PI. xcv, i.) 



5. Posterior two thirds of the presternum much compressed, but 

 not keeled. The anterior third is somewhat expanded, resembling 

 that portion of the presternum of Lininolagus. The first pair of ribs 

 is attached at the junction of the first and second fourths. The 

 mesosternal segments are more compressed laterally than they are 

 in the other skeletons and each succeeding one is a little shorter than 

 the one immediately in front of it. The xiphisternum is a trifle 

 shorter than the presternum, is comparatively short, and about 

 equally widened at each end. This type of sternum is found in the 

 single skeleton of Pronolagns. (PI. xcvi, 3.) 



6. The anterior portion of the presternum is considerably ex- 

 panded laterally, having a tendency to be intermediate in form be- 

 tween the presterna of Lepns and those of Ronierolagns and OcJio- 

 toiia. The mid-ventral line of this expanded part bears a low keel 

 which is not extended backward on the posterior portion of the 

 presternum. The first pair of ribs is attached to the middle of the 

 presternum. The mesosternum as a whole is wider than are the 

 mesosterna previously mentioned. It is also shorter, so that its 

 length is but little greater than that of the presternum or of the 

 xiphisternum, both of which are about equal in length. The first, sec- 

 ond, and third mesosternal segments are about equal in length ; each 



