340 E. L. Troxell — Palceolagus, an Extinct Hare. 



Art. XXII. — PalcBolagus, an Extinct Hare; by Edward 



L. Troxell. 



[Contributions from the Othniel Charles Marsh Publication Fund, Pea- 

 body Museum, Yale University, New Haven, Conn.] 



Among the many skeletons of the smaller mammals in 

 the Yale Fossil Vertebrate Collection there are numerous 

 specimens of the fossil rabbits and hares, some of which 

 comprise unusually complete skulls, limbs, and vertebrae. 

 Two distinct species of the genus Palceolagus Cope were 

 secured by Professor Marsh in the early days of verte- 

 brate exploration, one of them the smaller P. haydeni, 

 which varies considerably in size and age characters and 

 may be considered to include specimens of the subspecies 

 P. agapetillus, very small, and of P. intermedins, moder- 

 ately large. Distinct from it and widely separated is a 

 larger species apparently closely allied to P. turgidus. 



There is a most remarkable similarity between the 

 Recent hares and rabbits, and their ancestors in the 

 Oligocene. They evidently became adapted early to an 



Fig. 1. — Palceolagus haydeni. Cat. No. 10356, Y. P. M. Side view of 

 skull and jaws. Nat. size. 



environment which, relative to its great diversity, has 

 changed but little in the long lapse of time. Since their 

 habitat and habits have been identified with swamps, 

 plains, mountains — in fact, every conceivable condition 

 — no barriers seem to check them ; and because of their 

 wide freedom and constant intermixing, they have 

 changed but little since the time of Palceolagus in the 

 Oligocene. 



Generic characters. — As early as 1869 Joseph Leidy^ 

 drew attention to the distinction between the Recent and 

 Oligocene forms as shown by the three and two lobes of 



^ J. Leidy, Journ. Acad. Nat. Sei. Phila. (2), 7, 331-334. 



