1892.] POSITION OF NOTORYCTES TYPHLOPS. 365 



the Marsupials, Notoryctes, aud the Monotremes, and is morpho- 

 logically the same through which ruus the urine in the male Mono- 

 tremes. 



II. The shoulder-girdle of Notoryctes is built after the Marsupial 

 type ; it shows the complete absence of an interclavicle, of coracoids, 

 and of " epicoracoids." As confirmatory evidence of the affinities 

 of Notoryctes with the Monotremes, Mr. Ogilby mentions "the 

 considerable development of the clavicle, which is connected by 

 ligament to the sternal apparatus, along with the rudimentary 

 character of the epipubic bones being also Monotrematous." The 

 clavicles of Notoryctes are weak, their sleuderness of function is 

 obviously indicated by their long ligamentous connexion with the 

 manubrium sterni. In the Dasyures and in the Bandicoots the 

 clavicles are very rudimentary or even absent, while in the Mono- 

 tremes they are, by means of a large interclavicle, fastened to the 

 sternum as firmly as possible. " It may be sought to explain away 

 this difference in the strength of the shoulder-girdle on the grounds 

 that Notoryctes, Echidna, and Ornithorhynchus have the fore limbs 

 strengthened in order to enable them to burrow with the greater 

 ease ; but the superficiality of such a view is demonstrable at a 

 glance, if we take into consideration the fact that the Peramelidce, 

 which are also of fossorial habits, though not in so marked a degree 

 as the genera mentioned above, are absolutely without rudiments of 

 these bones." This may be, but the composition of the shoulder- 

 girdle and sternal apparatus of Notoryctes is one of the strongest 

 proofs against its Monotreme affinities. Its ancestors had lost the 

 very strength of the sterno-scapular and humeral support which is 

 so essential to an intensely fossorial animal, and its organism has 

 resorted to a new device of giving strength to the chest by an extra- 

 ordinary development of the first pair of ribs. The latter firmly 

 fix the anterior portion of the sternum and secure the development 

 aud working of strong pectoral and humeral muscles. A similar 

 case is afforded by the Dasypodidce. Is it more likely that a 

 burrowing, digging creature like an Echidna would give up its 

 strongly secured chest, or that a Marsupial (which as such had lost 

 coracoids and interclavicle, and obeys the general law that parts 

 once lost by reduction cannot be redeveloped) which assumes 

 strongly fossorial habits would resort to strengthening some of those 

 parts which it does possess, namely ribs, in order to attain a similar 

 result ? 



How the rudimentary character of the epipubic or marsupial 

 bones of Notoryctes can be used as evidence of its affinity to Mono- 

 tremes is not obvious, considering that in both Echidna and 

 Ornithorhynchus these bones are much stronger and larger than in 

 any Marsupial. 



III. The marsupium seems to be a permanent organ in the female 

 Notoryctes, and a pair of minute mammary prominences, devoid of 

 hair and ending in nipple-like projections, have been discovered by 

 Professor Stirling. This is likewise a Marsupial, not a Monotrema- 

 tous character. The pouch in Notoryctes opens backwards towards 



Proc. Zool. Soc— 1892, No. XXVI. 26 



