No. 580] ORIGIN OF SINGLE CHARACTERS 



I. Genus Canis II. Genus Alopex III. Genus Vulpes 

 Characters. — Skull Characters. — Skull Characters. — Skull 

 heavy and deep (depth intermediate in general slender and low 

 of brain-case more than form between that of (depth of brain-case 

 one-third condylobasal Canis ami Vnlpcs; occip- loss than one third 

 length) : interorbital re- ital depth about one- condylobasal length ) ; 

 gion thickened and ele- third condylobasal interorbital region 

 vated, the frontal si- length; interorbital re- nearly flat, the frontal 

 nuses rather large, the gion more elevated than sinuses scarcely in- 

 postorbital processes in Vulpes owing to flated, the postorbi- 

 thick, convex above, greater inflation of the tal processes thin, 

 their edges rounded off ; frontal sinuses; postor- slightly concave 

 dorsal profile of fore- bital processes thin, flat above, their edges 

 head rising rather ab- or slightly concave overhanging and 

 ruptly and noticeably above, with bead-like, bead-like; dorsal pro- 

 above level of rostrum ; overhanging edges ; dor- file of forehead ris- 

 dental formula : sal profile of forehead ing very slightly and 

 3-3 c l-l 4-4 rising abruptly above gradually above level 

 3-3' C l-1' pm 4-4' rostrum as in Canis; of rostrum; dental 



* 3 times in palatal 



.gated, the point of form £ox . life 

 >er tooth extending shorj n]l(| rn 

 •cely beyond middle ■'['•[ 



The fact that changes of proportion include the most 

 frequent characters while numerical changes include the 

 least frequent characters is again very strikingly brought 

 out in Miller's remarks on the origin of the domestic 

 dogs from the wolf (Canis lupus) : 



