39 



the digital specialization has proceeded so far, the manus has 

 not undergone the adult folding which makes the determin- 

 ation of the different elements a matter of some little diffi- 

 culty. It is well known that in his original communication 

 (1891) Sir Edward Stirling designated the specialized digits 

 as 4th and 5th, and assumed that the small digits were the 

 1st, 2nd, and 3rd. In the extended description published in 

 the same year this error was noted and corrected, and correct 

 figures were published. Despite this, Lucas and Le Souef 

 (1909) speak of "the edge of the large triangular nail of the 

 fifth digit" being used for digging. 





v.-.' ■ :'::-Ti(. ■ ■ 



Fig. 5. 

 Notoryctes typhlops. 

 Left lateral view of the caudal region. 



In the embryo the 1st, 2nd, and 5th digits of the manus 

 are represented by mere tubercles. It is a very remarkable 

 thing that the manus should attain one of its greatest 

 peculiarities by what is essentially an opposition of the 1st 

 and 2nd digits to the 3rd, 4th, and 5th, such as exists, for 

 instance, in Phascolarctos. 



The pes is short and spade-like, the digits ranged in very 

 primitive fashion, save that the 2nd is very slightly in 

 advance of the 3rd. 



The tail, so far, presents none of its adult peculiarities. 

 The external genitalia reveal to external examination only 

 a raised cloacal margin from which protrudes a genital 

 tubercle. No trace of a pouch rudiment, nor of an umbilical 

 site are visible externally. 



