LAGOMOBPHA. , 875 



PALiEOLAGUS HAYDENI Leidj. 



Proceedings Academy Pbilada., 1856, p. 89. Extinct Mamm. Dakota and Nebraska, p. 331. Cope, Ann. 

 Report U. S. Geol. Surv. Terrs., 1873 (1874), p. 478. American Naturalist, 1883, p. 172. Palceo- 

 lague agapelillua Cope. Paleontological Bulletin No. 15, p. 1 (Aug., 1873). Annual Report IT. 

 S. Geol. Surv. Terrs., 1873 (1874), p. 478. 



Plate LXVI; figs. 1-27. 



The dentition of this rabbit has been fully described by Professor Leidy, 

 but the material at the disposal of this distinguished naturalist did not enable 

 him to furnish either the cranial or skeletal characters. My numerous 

 specimens enable me to supply this deficiency. It is, however, to be ob- 

 served that I cannot associate the skull with a skeleton as belonging to the 

 same individual in any instance. The characteristic marks of the Leporidce. 

 in all the bones of two species found mingled in profusion with the jaws and 

 teeth of the P. haydeni and P. turgidus, in corresponding numbers, render 

 their correlation sufficiently certain. 



The form of the muzzle seen from above is that of an obtusely trun- 

 cated wedge. The contraction in the width of the nasal bones forward is 

 very slight ; at the extremity they are strongly convex, while the posterior 

 region is flat. The canthus rostralis is sharp, consisting of the narrow rib- 

 like maxillary prolongation of the premaxillary bone, which at its anterior 

 third is a little more elevated than the adjacent portion of the nasal bones. 

 Its posterior apex does not extend quite so far posteriorly as that of the nasal 

 bone, and the frontal sends a wedge-shaped prolongation to the outer side 

 of it, which extends as a narrow splint anteriorly between the premaxillary 

 and maxillary. The rugose patch of the maxillary extends more than half 

 way towards the alveolar border of the superior incisors, and is bounded in 

 front by the maxillo-premaxillary suture. It is separated from the orbit 

 behind by a band of dense bone. The foramen infraorhitale exterius issues 

 entirely below the rugose patch. The maxillo-premaxillary suture crosses 

 the palate a little behind the middle point between the incisor and first 

 molar, and on the side above the diastema bounds a long process forward. 

 It then returns to the inferior border of the rugose patch, inclosing a notch 

 with the inferior border of the same. The palatine bones are flat and 

 occupy more than half the palate between the molars. Their common 

 suture is at least as long as that of the maxillaries, and extends as far for- 



