304 ZAGLOSSUS. 
Although there are normally three functional digits on each foot, six cases 
are recorded in which there are more than this number. These are to be con- 
sidered as regressive variations to the five-clawed condition as seen in the 
Echidna. Only one case is known in which there were five claws on each foot. 
The validity of the genus Zaglossus for the Proechidna as distinet from 
Tachyglossus for the Echidna has been questioned, but as modern generic con- 
cepts go, they may well be kept apart. The chief characters of Zaglossus are: 
— (1) the great elongation and depression of the rostrum, with the accompany- 
ing greater development of the tongue and salivary glands; (2) the usual pos- 
session of but three functional claws on each foot, correlated with important 
differences in certain of the muscles of the fore and hind legs; (3) the outline 
of the distal end of the humerus is very different from that of the Echidna, with 
a broad, evenly rounded inner tuberosity and a shallower notch at the ental side 
of the articulating surface; (4) the spines are more solid with a relatively small 
lumen in contrast to the thin-walled spines with large lumen of the Echidna. 
The Proechidna represents a more highly specialized type than the 
Echidna. 
