1892.] POSITION OF NOTORYCTES TYPHLOPS. 363 



However, let us return to facts. Notoryctes occurs in the very 

 middle of Australia, and every important part of its anatomy is 

 known. Its teeth are not like those of any known Edentate, 

 although they are aberrant enough in number and position even for 

 Marsupials. It possesses a marsupium and an inverted inner 

 angular process of the under-jaw — two characters which are 

 together sufficient to prove that Notoryctes is a member of the 

 Marsupialia or Metatheriain tlie sense hitherto defined and accepted. 



Mr. Douglas Ogilby ' has naturally and correctly placed Noto- 

 ryctes as a separate family among the Polyprotodontia of the 

 Marsupiaha, but he hopes that " we have now obtained a definite link 

 between the Proto- and Metatheria subclasses, a link which will 

 perhaps eventually bridge over the gulf which at present separates 

 the Monotremes from the Marsupials." A definite link would 

 certainly, not perhaps eventually, bridge over that gulf, but unfor- 

 tunately that much hoped-for link is still missing ; certainly it is not 

 represented by Notoryctes. 



The Monotremes are characterized by the possession of: — (1) a 

 typical cloaca ; (2) a Saurian shoulder-girdle, i. e. an episternum 

 or interclavicle, clavicles, complete coracoids, and considerable 

 remnants of the ventral halves of precoracoids (epicoracoids of some 

 authors). Additional characters are :— (i) absence of functional 

 teeth in the adult; (2) a temporary marsupium without nipples. 



Notoryctes differs in every one of these four points from the 

 Monotremes and agrees with the Marsupials. 



I. The cloacal arrangement appears at first sight strikingly like 

 that of the Monotremes. The accompanying drawings (see p. 364) 

 will explain the points better than a lengthy description. It must 

 be borne in mind that there are Metatheria without a functional 

 marsupium, while in the Prototheria this organ is functional ; like- 

 wise there are monotrematous mammals besides the Prototheria. 

 Marsupium and cloaca, taken alone, are therefore not sufficiently 

 diagnostic for the separation of Proto- and Metatheria : they are 

 differences of degree only, the intermediate links being furnished 

 by the various Marsupialia themselves. I have shown elsewhere ■ 

 that in the Marsupialia the urogenital and rectal openings are not 

 completely divided off by a partition, there being still one common 

 external opening which leads into a common, although mostly 

 shallow chamber, viz. into the proctodseum or vestibulum cloacae. 

 In both male and female Marsupials (figs. 4 and 6, p. 364) the 

 urogenital sinus is still of considerable length, and is completely 

 shut off from the rectum, while in the male Monotremes (fig. 1) the 

 urine passes into a urodseum, or middle chamber of the cloaca above 

 the penis. In Notoryctes and in all other Marsupials, this separate 

 exit of the urine and of the genital products is made impossible by the 

 completion of the fold F, Urine and sperm pass through the penis 

 in the male, and in the female the ovarial products (eggs or foetus) 

 have the same channel as the urine. This channel is the same in 



' Advance copy of portion of ' Handlist of Australian Mammals,' issued 

 July 31st, 1891 : Sydney. 



^ " Eemarks on the Cloaca and on the Oopulatory Organs of the Amniota," 

 PhU. Trans. 1887, pp. 5-37, pis. 2-5. 



