373 



4 are well developed and normal. It is to be noted that 

 syndactylism does not destroy the primitive mammalian dis- 

 tribution of the interdigital pads. The hypothenar pad 

 becomes flattened in older examples. 



External Genitalia. — The genital tubercle of the male is 

 at first freely exposed beyond the limits of the cloaca (see 

 fig. 13). In later stages the tubercle becomes hidden from 

 the surface by its own retraction within the cloaca and by the 

 upgrowth of the cloacal margins (see fig. 14). 



Two mammary areas disposed bilaterally exist within the 

 pouch of the female (see fig. 15). 



^^^•^'^ 





I. 



Fig. 15. 



The pouch and mammary glands of the female at the 100 mm. stage 



(from Specimen female B, Perth Museum). 



DESCRIPTION OF PLATES. 



Plate XIV. 



' Pouch young of Trichosurus vulpecula, var. typicus, 



photographed against a background of ^ j ^o-inch squares. 

 Specimen male A, Perth Museum. B, Specimen male C, Piper. 



Plate XY. 



Pouch young of Trichosurus vvlpecula, var. typicus, 

 photographed against a background of Via-i^^ch squares. 

 C, Specimen female B, Perth Museum. 

 I), Specimen male D, Perth Museum. 



