OF THE AUSTKALIAN MAESLTJALIA. ICO 



appears to represent the hallucal pad of Fhascogale. Digital pads are present as in the 

 latter genns ; they are well developed and separate. Each pad has a punctate area at 

 its tip, pi'ohably representing a formerly striated surface. The first digital pad tends to 

 be approximated to the second, as in some syndactylous forms. 



The derivation of the type met with in Thylacinus is quite as obscure. The 

 modification is a digitigrade one, as in the smaller terrestrial forms. The foot is not 

 greatly elongated, the proportion being in the neighbourhood of 1:4. The hallux is 

 absent, as in other advanced terrestrial forms. A single large pad, placed at the bases 

 of the digits, shows signs of trilobate structure, and may have originated from the fusion 

 of three separate pads, as in smaller forms. It is difficult either to demonstrate a 

 connection of this type with those represented by other members of the family, or even 

 to prove that it is of arboreal derivation. 



PHALANGEEIDJ3. 



In this family the same general principle is exemplified as in the arboreal line of tlie 

 Dasyuridae. We have a series of animals showing increase in size of body and pro- 

 gressive chai'acters in other respects, but with foot-patterns of much the same type 

 throughout. The modification is an arboreal one, and in some respects more primitive, 

 in others more specialized than in the primitive Dasyurida?. Just as in the case of the 

 dentition, the exact prototypal characters are not found associated in any single form, 

 but are distributed over two families — in this case, the present one and the Dasyuridae. 



The pes of Dromicia (PI. 7. fig. 13, Z>. nana) may be taken as representing the 

 prototypal condition not only for the Phalangeridae, but for all of the Australian families 

 with the exception of the Dasyuridse. The general characters are those of the second 

 arboreal phase [cf. p. 163). The primitive characters, as compared with the Dasyuridse, 

 are: (a) the short broad proportions of the foot and the radiating character of the digits ; 

 (6) the unreduced chai'acter and wide opposability of the hallux; [c) the more typical 

 development of the five striated plantar pads and of the terminal pads of the digits. 

 The more advanced characters are : {a) the great development of the fourth toe * ; (6) the 

 reduction and syndactylism of the second and third toes. 



In the remaining members of the family, excepting Tarsipes, the modific<ations of this 

 type are few and insignificant. Acrobatcs pygmcem presents the same conditions as 

 Dromicia nana, except that there is an accessory pad on the postero-external side of th<i 

 hallucal pad and another smaller one on the outer side of the third digital pad. 'Tarsipes, 



* With reference to the recognition of the enlarged nature of the fourth toe as an arboreal adaptation (Wingc, 

 Bollo), it is interesting to note that a different explanation was given b\' Owen ( 1879). While acknowledging ttie 

 fact that there has been a successive enlargement of this member in the Macropodida;, Owen considered its original 

 predominance to be a reptilian character. A somewhat similar opinion has been expressed by Leche (1891). This 

 writer remarks as follows : — " Bis auf Weiteres neige ich zu der Ansioht hiii, dass die Prevalenz der 4. Zehe hni 

 Marsupialia ebenso wie diejenige der 3. bei Ungulata unabhangig von der besondern Function durch Vererbung 

 erworben ist." 



