135 



remain ununited, and it might be said that a most primitive type of anterior 

 nares was grafted on to a most highly speciaHzed type of rhinarium. The lower 

 extremity of the mesial nasal process falls considerably short of the line of the 

 upper lip, so that the animal may be said to have a well-marked median "hare- 

 lip." The whole rhinarium is clothed at this stage by very minute down hairs, 

 and its surface is finely punctate. In consequence of the presence of these fine 

 down hairs, Pocock has been led into making the rather rash assertion that "there 

 is no true rhinarium," a rather curious descriptive phrase for the animal which 

 has the most conspicuous rhinarium of any marsupial. The dorsal shield-like 

 expansion reaches caudad slightly past the anterior canthus of the eye. 



The External Ear. — At this stage the external ear already shows the curious 

 hair-covered flap-like appearance that is so characteristic of the adult. The concha 

 is hairy both within and without, and a conspicuous tuft springs from the crus 

 of the helix. There are here developed two genuine tragoid projections — 

 genuine in the sense that they spring from the helix and not from the antihelix. 

 These true tragoid projections are marked x in fig. 5. The antihelix is well 

 developed, and at the middle of its length it is inflected and folded upon itself, 

 so that it might be said that a superior and an inferior processus antihelicis were 

 present, though neither upper nor lower portion can rightly be termed a processus. 

 Of the adult condition of the auricle Thomas says, "The metatragus is almost 

 obsolete," and by metatragus he doubtless refers to the superior part of the 

 antihelix. In Pocock's description of the ear of the adult, and in the comparison 

 of it with that of Trichosurns vulpecula, the homologies of the various anatomical 

 parts of the concha are not appreciated in consequence of the limitation of the 

 examination to adult material only. The inferior portion of the antihelix is 

 bounded behind by a depression which constitutes a wide but shallow bursa or 

 sulcus auris posterior. The auricle of Phase olarctiis at this stage presents a 

 strange and interesting admixture of characters which can only be interpreted by 

 reference to forms not yet described in this series of papers. 



Manus. — The digital formula is 4>3>5>2>1. The manus presents 

 the characteristic feature of the opposition of digits 1 and 2 to digits 3, 4, and 5 ; 

 a condition which leads to a peculiar broadening of the palm in its proximal 

 part. The first digit is not in any way specialized. The apical pads are well 

 developed, and are striated ; but the striations are not particularly deeply 

 sculptured or conspicuous. The rest of the palm is granular, and although 

 a linear arrangement of the granulations is apparent, no definite striations are 

 formed in any part. The palmar pads are not well defined. The manus is 

 relatively very large. All digits are armed with strong curved claws. 



Pes. — The digital formula is 4 > 3-2 > 5 > 1. The syndactylous digits are 

 extremely well developed, being longer than the fifth digit and nearly as long 

 as the fourth. Digit 1 is short and greatly broadened ; it possesses no nail. 

 Strong curved claws are present on all the other digits. The apical pads are well 

 developed and striated. The whole of the sole is granular from the bases of 

 the apical pads to the back of the heel. Plantar pads are not well developed. 



External Genitalia. — The cloacal papilla is prominent and the genital tubercle 

 is just exposed within its orifice in this example. 



References:— -(1) Oldfield Thomas, Cat. Brit. Mus., 1888, p. 209; (2) 

 Pocock, R. I., Proc. Zool. Soc, 1921, pp. 591-607. 



EXPLANATION OF PLATE X. 



Phascolarctus cinereus. 

 Pouch embryo from Queensland Museum, 110 mm. in R.V. length. SHghtly enlarged. 



