266 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



wear, are in contact by their opposed angles, and at lengtli become 

 confluent in a common disk. The angular expansions of the disks 

 are the modified homologues of the flanking tubercles of the Masto- 

 dons; and as the character prevails in several forms among the 

 latter, its presence in so pronounced a degree in the African Ele- 

 phant might have led us a priori to expect in nature other allied 

 species in which it would be more or less exhibited. Premolars 

 have not as yet been observed among the teeth of this species. 



3. E. (Loa-odon) planifrons. — In order show the constancy of the 

 hypisomerous character of the ridge-formula among the Loxodons, as 

 furnishing a reliable aid in the distinction of certain of the European 

 fossil Elephants, it is necessary to refer briefly to the dentition of 

 another form in the subgenus, being the Indian extinct species from 

 the Sewalik Hills, E. {Loa\) planifrons, the characters of which, 

 yielded both by the skidl and teeth, are so i^ronounced, and the 

 accessible materials in European collections so abundant, as to place 

 its specific distinctness AvhoU}' beyond question. In this form the 

 ridge-formula of the deciduous and true molars is thus : — 

 Milk-molars. True molars. 



3 + 6 + 7 7 + 8 + 10 



3 + 6 + 7. 7+ + 



Vertical sections of an upper and lower true molar contrasted with 

 corresponding teeth of the African Elephant are shown by figs. 5 a 

 and 5 6 of pi. 2 of the ' Fauna Antiqua Sivalensis.' The ridges 

 are seen to be much more elongated vertically than those of E. 

 (Steg.) insif/nis, figs. 6 a and 6 6, but to be considerably less so than 

 in the African Elephant, figs. 4 a and 4 b. Other distinctive cha- 

 racters from the latter species consist in the enormous quantity of 

 cement which fills up the valleys and envelopes the ridges, and in 

 the much greater thickness of the folded plates of enamel. When 

 the teeth are regarded from the crown aspect, the disks of wear 

 assimilate more in general form to those of the existing Indian 

 than of the African Elephant. They form transverse bands, which 

 are broader, fewer in number, and wider apart than in the Indian 

 Elephant, sometimes M^ith the bounding edges of enamel nearly ' 

 parallel, in other cases showing a slight angular expansion, or 

 throwing out a salient loop (outlying tubercle) near the middle, as 

 in figs. 8 and 9 of pi. 14, but never exhibiting the systematic 

 lozenge-shaped expansion so characteristic of the African Elephant. 

 The enamel edge or macliarris is very thick, and generally free from 

 plaiting. The tips of the digital processes are tiiick, and yield well- 

 marked circular disks before they become confluent by wear. These 

 characters are represented throughout by the figures of plates 11 

 and 12 of the ' Fauna Antiqua Sivalensis,' which include the prin- 

 cipal varieties in the form of the molar crowns. 



Of the difl'erent teeth in the upper jaw the antepenultimate upper 

 milk-molar is represented by fig. 1 of pi. 12 of the 'Fauna Antiqua,' 

 and in vertical section by fig. 1&, showing three principal ridges, with 

 a basal ridgelet in front, and a hind talon. The penidtimate milk- 



