1882.] MR. W. N. PARKER ON THE INDIAN TAPIR. 775 



entirely within their sockets. The last upper and lower deciduous 

 molars had evidently only just come into place. 



De Blainville ' gives a description of several stages in the develop- 

 ment of the Tapir's teeth ; hut he is not at all clear on oue or two 

 important points, which I now hope to explain. 



On cutting into the jaws, distinct germs of the first and second 

 premolars were seen, in the form of small conical cups, one for each 

 main cusp ; and of these the second in the lower jaw were the 

 largest. There were no traces of the third or fourth premolars. 



It is a general rule amongst mammals that the first premolar 

 has no predecessor, or else, perhaps, that this tooth is really a per- 

 manent milk-tooth, the only exception usually given to this rule 

 being in the case of Hyrax^. In reference to the former of these 

 views, it is well known that there is a tendency in many mammals 

 towards the suppression of the milk-teeth, as, for instance, in the 

 Rabbit^ this being carried to an extreme in Marsupials, as Prof. 

 Flower has shown', and (as far as is yet known) in the Guinea-pig, 

 in which animals the last is the only one left. On the other hand, 

 as will be seen later on, the fact that in the Tapir the first milk- 

 molar is considerably larger than its successor might be taken in 

 support of the first view. It is thus interesting to find a more 

 primitive condition in the dentition of animals like the Tapir and 

 Hyrax. 



A comparison of the dentition of the young with that of older 

 animals is instructive. As in the Horse ' and other Ungulates, the 

 last deciduous molar remains functional for a long while, probably 

 for some time after the animal is fuUgrown ; and it can be at once 

 distinguished by its worn appearance. 



The first molar of the Horse appears long before the milk- 

 molars are shed, and, by the time all the permanent teeth have 

 appeared, is considerably worn. Thus an examination of a Tapir's 

 skull in which, though apparently adult, the last milk-tooth had not 

 been shed, might easily mislead one, and give the idea that there 

 were only three premolars above and two below. 



That this is not the case is proved by the skull of an x^merican 

 Tapir in the Biological Museum of the Normal School of Science, 

 to which Prof. Huxley has drawn my attention. In this, thouo-h 

 apparently a nearly adult animal, the last milk-molars above and 

 below were still functional, and above them, in the sockets, are the 

 teeth which were destined to take their place. Prof. Huxley has 

 also kindly allowed me to make a section of the jaw of an Indian 



' ' Osteograpliie,' tome iii. 



• Both de Blainville and Owen (Odontography, p. 605) state that in the Tapir 

 the first deciduous molar is succeeded by a permanent one ; but some doubt is 

 thrown on this conclusion by Huxley, in his ' Comparative Anatomy of Verte- 

 bi-ated Animals,' p. 3(55. 



3 See footnote on page 655 of Prof. Huxley's article " On the Application of 

 the Laws of Evolution to the Arrangement of the Vertebrata," P. Z. S. 1880 



* Phil. Trans. 1867. 



5 Prof. Owen states (Odontography, p. .581) that in the Horse the last deci- 

 duous molar is usually not shed until the last true molar has appeared. 



