SUMMARY AND CONCLUSIONS. 303 
descriptions of the five described forms or species of the Proechidna, the con- 
clusion is reached that all are referable to a single living species, namely Zaglos- 
sus bruijnii, of New Guinea, and that the various nominal races are based on 
individual variations due to age, wear, albinism, or individual differences in pig- 
mentation and molt. 
On account of the size and conformation of the humerus figured for the 
extinct Echidna owenii of New South Wales, it seems that this animal should be 
referred to the genus Zaglossus, thus establishing the occurrence of both Zaglos- 
sus and Tachyglossus, the Proechidna and the Echidna, in Australia as well as 
in Papua. 
The musculature is essentially like that of the Echidna, but that of the limbs 
shows important differences correlated with the reduction of the functional 
digits from five to three. Thus the fleror profundus digitorum sends tendons 
to digits 2, 3, and 4 only, and no trace is left of the additional tendons to 1 and 5 
that are present in the Echidna with its five-clawed manus. There is also in 
the hand a muscle apparently representing the abductor digiti quinti, which seems 
to be absent in the Echidna. The adductor longus is present in the hind leg of 
the Proechidna but apparently is lacking in the Echidna, and a small muscle 
probably representing a flexor longus hallucis is also found, but is absent in the 
Echidna. 
In correlation with the elongation of the beak, the tongue and salivary 
glands are more developed in the Proechidna. No second portion of the sub- 
maxillary gland was detected. There is a common duct by which the 
gall-bladder and the pancreas enter the intestine, not two separate ducts as 
described for the Echidna by Chapman. 
The supposed differences in vertebral formulae between the Proechidna 
and the Echidna are shown to be unreliable. Both exhibit a considerable degree 
of individual variation. A study of the young skull reveals several interesting 
peculiarities, such as a small median bone formed posteriorly between the frontals 
and here called interfrontal. The nasals are shut off from the external narial 
opening by the meeting of the premaxillaries in front of them. The zygomatic 
arch is shown to be formed mainly by an enormously expanded jugal, and the 
squamosal, which has been supposed to form the arch is really covered by the 
jugal and forms part of the brain-case as usual. The temporal canal of existing 
monotremes is merely the remnant of the temporal fossa, largely closed over by 
the expansion of the jugal dorsally. A ventral expansion of the jugal lines 
the glenoid cavity of the jaw. 
