ORDINAL TYI'KS OF MOLARS: CAKNIVORA 131 



stages leading to this secondary basin-shaped formation arc c;ird'ully 

 examined it will be found that they invariably point back to a more 

 symmetrical tritubercular arrangement. A similar case occurs in the 

 Microcheiroptera in the genus Arfil^ii* (Fig. 82), where the first and 

 second inferior molars ' have become basin-shaped and irregularly cuspi- 

 date remotely resembling the Microlestes molars (p. 102). The nearest 

 relatives of this genus are plainly tritubercular. 



According to Mivart and Gidley certain bats show a secondary 

 simplification of the molar pattern by fusion of the para- and metacones 

 as in the supposed case of the Zalambdodont Insectivores. 



In general, therefore, the Cheiroptera definitely support the tri- 

 tubercular theory, since the molar teeth are clearly derivable from 

 simple tritubercular types such as we find among the Insectivora. 



SPECIAL REFERENCES. 



Bronn, Klassen u. Ord. d. T/tierreichs, Bd. I., pp. 211-2:23. 

 Owen, R., Odontography, 1840-45. 

 Giebel, C. G., Odontographie, 18.".."). 



Schlosser, M., Die Affen . . . Clriropteren . . . dex Europaischen Tertiurs, 

 etc. Wieu, 1887-90. 



Allen, H., "A Monograph of the bats of North America," Bull. U.S. Nat. Mus., 

 No. 43. Washington, 1893, p. 198, 38 pll. 



Matschie, P., Die Megacheiroptera des Berliner Museums fur Naturkunde. Berlin, 

 1899. (This monograph contains 14 fine lithographic plates on the skull and 

 body-form of the Fruit-Bats, Pteropodidse.) 



CARNIVORA. 



The carnivorous quadrupedal placenta! mammals may be divided 

 into three grand divisions, namely : 



The Creodonta, which were primitive Carnivores of Cretaceous 

 and Lower Eocene age, the special peculiarity of which is that the 

 carnassial or specialized cutting teeth in the upper and lower jaws 

 are not the same as those in the true Carnivora. In the true 

 Carnivora invariably the fourth upper premolar and first lower 

 molar are transformed into carnassials ; whereas in the Creodonta 

 one or more of their first, second, and third upper and lower true 

 molars may transform into carnassials. The second great division is 

 the Fissipedia, including the modern terrestrial Carnivora, which 

 have been termed Carnassidentia by Wortman, in reference to the 

 distinctive possession of sectorials formed out of the fourth upper 

 premolar and first lower molar. The third great group is the 

 Pinnipedia, the water living forms, in which the teeth have been 



J H. Allen, "A Monograph of the Bats of North America," Bull. U.S. Xat. Mus., 

 No. 43, 1893, PI. V. 



