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 

 indi\'idual 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 estabHshing 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 iniportant differences correlated with the reduction of the functional 

 digits from five to three. Thus the flexor 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 vertel^ral 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 

 pecuharities, 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. 



