184 MAMMALIAN DESCENT. [Lect. VII. 



the ordinary annulus (tymjDanic or proper l)one of the 

 drum). 



3. Besides an anticip>ation of the carnivorous type of 

 skull, there are plain and evident memorials of that 

 of the Marsupial ; for the ali-sphenoids each give off a 

 trumpet-shaped process to enhirge the cavum tympani 

 or cavity of the ear-drum ; a most diagnostic character 

 in the Metatheria. 



4. I have already spoken of a very peculiar structure 

 seen in many of the Australian Marsupials, namely, that 

 the posterior paired vomers are large, for they meet 

 behind the moderate-sized middle-piece ; this is well 

 seen in Rhynchocyon ; there are several more characters 

 equally marsupial. 



5. The very diagnostic tympanic wings of the basi- 

 sphenoid are absent in this peculiar Insectivore. 



6. The pre-sphenoid or third basal beam-bone is 

 distinct, as in Marsupials and Rodents. 



Thus this greatly specialised kind of Insectivore, whilst 

 retainins; the most marked characteristics of the Meta- 

 therian skull, takes on two characters, one of which, had 

 it become dominant, would have landed it amongst the 

 Proboscidea or Elephants, whilst the other would have 

 made it a Carnivore. It attempted too much at once, 

 and thus, like a man in doubt, it made but little j^rogress ; 

 moreover, in this developmental shilly-shallying, it failed 

 to drop the old Marsupial, to take on the new Eutherian, 

 nature, and was thus in danger of going out of being 



