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Show 38 MR. M. F. WOODWARD ON THE [Jan. 5, 4. On the Milk-Dentition of Procavia (Hyrax) capensis of the Rabbit (Lepus cuniculus), with Remarks on the Relation of the Milk and Permanent Dentitions of the Mammalia. By M. F. W O O D W A R D , Demonstrator of Zoology, Royal College of Science, London1. [Eeceived January 5, 1892.] (Plate II.) 1 I. Historical. The dentition of such an interesting Mammal as Hyrax, as may readily be supposed, has been carefully studied by many zoologists, who, probably owing to the fact that many of them based their descriptions upon one or two dried skulls only, have given the most varied interpretations of the teeth. As a result we find a great discrepancy in the dental formulse given in their various monographs and in the text-books compiled from them. Most of the earlier authorities agreed as to the absence of canines, but disagreed as to the total number of teeth present (viz. 34 or 36) and as to the number of true molars and incisors, the most commonly accepted formula being i. ^ c. ^, pm. -, m. f = 3 4 . Many observers, however, state that there are present at one time 8 cheekteeth above, and as they regard the extra tooth as a molar, they formulate the molars as 3-4 above and 3 below. More rarely we find the incisors described as being ~ ; and lastly, two observers 2 have described a pair of canines as being present in the upper jaw. All are agreed as to the number of teeth present in the lower jaw of the adult, viz. 9 ; but there is much disagreement as to the total number of teeth present in the upper jaw (viz. 8-9), and also as to the homologies of the individual teeth and sets of teeth. Most state emphatically that there are no canines present in either jaw. Cuvier, however, asserted (4) that there was a pair of small canines present in the upper jaw of the young animal, and he regarded them as the accessory teeth of Pallas (25), but this opinion he afterwards retracted (5). It remained for Lataste (19) to be the first to show definitely that there is present in the upper jaw of all young specimens a pair of small canines; he has shown that these are shed early in life and that they rarely persist til! the completion of the second dentition. He bases his conclusions on the shape and position of these teeth together with the characters of the 2nd maxillary tooth (1st premolar) as exemplified in a very large series of skulls of all ages, and finally on a comparison with the teeth of the near allies 1 Communicated by Prof. Howes. 2 Cuvier (4) and Lataste (19). |
