OF THE AUSTRALIAN j\[AESUPIALIA. 167 



In Sminihopsis hirtipes (PI. 7. fig. 5) we find what is apparently another modification 

 of the condition in S. larapiiiia. The proportion of breadth to length is 1 : 6-3, the foot 

 being relatively shorter than in the preceding species. The hallux is more reduced than 

 in S. lampinta. The liallucal pad is represented by a small protuberance. The digital 

 pads are more specialized than those of the preceding species, being so completely fused 

 together that their former distinctness might be questioned were it not for the fact that 

 the compound structure shows a trilobate contour. 



In Antechinomys laniger (PL 7. fig. 6), which is the final member of the sei'ies, we 

 find a further advance on S. crassicaudata. The proportion of breadth to length is 

 1 : 10. The hallux is absent, as are also the hallucal and marginal pads. At the bases 

 of the outer digits there is a single large pad representing the now completely fused 

 pads of the more primitive forms. The whole surface is covei-ed with granules, which 

 increase in size towards the apex. The posterior portion of the sole is completely hairy 

 as far forwards as the base of the digital pad. 



A second line of terrestrial evolution, with relations with the larger instead of tlio 

 smaller species of Phascogale, is represented by Chcetocercus crlsticauda and Dasj/aroides 

 Byrnei. These forms repeat, on a larger scale, the special modifications found in 

 Sminthopsis. In Chcetocercus (PI. 7. fig. 8) the proportion of breadth to length is 

 1 : 4'53, much the same as in Phascogale. The hallux is more minute than in the latter 

 genus. The hallucal pad is represented only by a small protuberance, bearing gi-anules 

 which are slightly larger than those of the surrounding surface. The digital pads are 

 well developed, but are laterally compressed and fused at their bases : their surfaces 

 are entirely granular ; but, as in ^S'. crassicatidata, there is an enlarged apical granule 

 representing a formerly striated area. The middle line of the plantar surface is hairy 

 for about 10 mm. posteriorly. 



Basyuroldes Byrnei (PL 7. fig. 9) shows an advance on the preceding species. The 

 proportion is 1 : 7'5. The hallux is absent, as are also the marginal and hallucal pacLs. 

 The digital pads are well developed and fused basally. As in Chcetocercus, their surfaces 

 are granular, and a larger apical granule is present ; the latter shows signs of transverse 

 striation. The sole is hairy for 10 mm. posteriorly, as in the latter species, and the 

 marginal hairs of both sides of the foot, as far forwards as the pads, tend to encroach 

 on its granular surface. 



s' 



Within the genus Dasytn-us we find both arboreal and terrestrial phases. In 

 Basyurns hallucuius (PL 7. fig. 10), the smallest and most primitive of four species*, 

 we find an arboreal foot type which is scarcely distinguishable from that of Phascogale. 

 The proportion of breadth to length is 1 : 37. All of the pads are well developed and 



* The collection contains no examples of the I'apuMii form. /-*. albopw\etatnt. 



