OF THE CANIDA AND URSIDA. 923 
so that the foot is extraordinarily wide when spread to the fullest 
extent, the third and fourth capable of being separated until the 
inner edges of the pads are in a transverse, almost straight, line 
with the border of the web connecting them which is only lightly 
emarginate, the width of this web about twice the length of one 
of the pads and exceeding the distance between the pads of the 
second and third or fourth and fifth digits. Claws long and 
slender. The hairs on the lower surface of the foot abundant, 
silky,and long, completely concealing the pads when undisturbed. 
Hind foot very like the fore foot, but smaller, the posterior 
portion of the plantar pad more overgrown with hairs. 
The rhinariwm is rectangularly rounded in front in profile ; 
from the front view its upper edge is wide and straight with 
nearly rectangularly rounded angles, its inferior border is 
mesially angular with obliquely sloping, slightly sinuous sides, 
the area below the nostrils being moderately deep in front and 
narrow posteriorly below the slit; the hairy area of the lower 
lip below the rhinarium in front is moderately deep and the 
cleft is continued upwards as a shallow groove between the 
nostrils. 
The facial vibrisse are long and abundant and normal in 
position, about six superciliaries, three interramals, and three to 
each of the genal tufts. Im an example of Ps. azaricus from 
Mar del Plata, the vibrissee resemble those of the species above 
identified as Ps. gracilis. 
The feet of Ps. gracilis suggest adaptation to desert conditions, 
the spread of the digits and the thick hairy clothing preventing 
sinking in the sand. 
It will be interesting to see in the future to what extent the 
feet of the other fox-like South American dogs, suchas Ps. culpeus, 
conform to this type, which differs so widely from that of some 
of the true foxes of the Old World, like Vulpes and Otocyon. 
Alopex lagopus. 
(Text-fig. 7.) 
A single old female specimen of 4. lagopus spitzbergensis. 
The feet differ from those of all the species of Canide 
examined in the presence of a distinct thickish ridge of integu- 
ment, passing forwards from the median lobe of the plantar pad 
to the area behind the point of junction of the third and fourth 
digits, and dividing the glandular depression between the digital 
and plantar pads into right and left portions. Moreover, the 
area of the integument on the proximal side of the digital 
pads is thickened and cushion-like, not gradually sloped away, so 
that the partially divided depression is bordered in front and 
laterally by elevated walls, making it appear deeper than in other 
species. The median longitudinal ridge of skin is not so high as 
the plantar pad and as the thickening behind the third and fourth 
Proc. Zoou, Soc.—1914, No. LXII. 62 
