xvri] THE COMPARISON OF RELATED FORMS 1079 



_2_.i r_.l_ »_ .7_8 



and to the same scale of magnitude; B-G, various artificial or imaginary- 

 types, reconstructed as intermediate stages between A and H; M, skull of 

 Mesohippus, from the Oligocene, after Scott, for comparison with C; P, skull 

 of Protohippus, from the Miocene, after Cope, for comparison with E; Pp, 

 lower jaw of Protohippus placidits (after Matthew and Gidley), for comparison 

 with F; Mi, Miohippus (after Osborn), Pa, Parahipptis (after Peterson), 

 shewing resemblance, but less perfect agreement, with C and D. 



