CHARACTERS OF EUELEPHAS. 145 



divided into two subordinate series, namely, the ' Eurycoro- 

 nine,' in which, the molar crowns are broad, the ridges trans- 

 verse, and the valleys open ; and the ' Stenocoronine,' in which 

 the crowns are narrow, and the valleys are obstructed by outly- 

 ing tubercles. These two types, under peculiar modifications, 

 are equally present among the forms referable to Euelephas, 

 and the distinctive marks upon which they are founded furnish 

 excellent help in determining the distinctness of the species. 

 They are in some respects nice in degree, but at the same 

 time, like all well-founded distinctions in nature, they are 

 very constant. In order to facilitate the determination of 

 the ridge-formula in the fossil forms, the characters of the 

 teeth in the existing species will first be considered. But it 

 is necessary to give some preliminary explanations of the 

 modifications of the dental characters in the molars of the 

 Euelephants, and of the terms that are here used to express 

 them. 



The folded crown of the molars in the groups Trilophodon, 

 Tetralophoclon, and Stegodon is composed of three or more, 

 regularly or irregularly transverse, wedge shaped cores of 

 ivory, arising from a common base, and covered by a shell of 

 enamel, which is uniformly reflected over their apices and 

 over the re-entering angles at their base. These divisions 

 are called ' ridges ' or ' colliculi,' and the interstices or 

 valleys between them ' valliculse : ' though usually open in 

 the Mastodons, the latter are in the Stegodons occupied by 

 an enormous mass of cement, forming reversed wedges in 

 relation to the ivory-cores. The layer of enamel thus alter- 

 nates with the ivory and cement, and, being of uniform 

 thickness throughout, it is the only portion of the crown 

 materials to which the terms ' plate,' ' lamina,' or ' lamella ' 

 can with propriety be applied. 



In the groups Loxodon and Euelephas these ridges go on 

 increasing in number, without a corresponding augmentation 

 of the length of the crown, so that the penultimate true 

 molar (or last of the intermediate series), which in the 

 Trilophodons has only three ridges, in the Indian Elephant 

 presents five times that number, or about sixteen ridges. 

 The law of compensation (' balancement ' of the French, and 

 ' anamorphosis ' of some German authors) comes into play 

 to make the necessary adjustments. The ridges are com- 

 pressed and close-packed, with an attenuation of the con- 

 stituent ivory, enamel, and cement materials ; but as there is 

 a limit to the lateral extension of the crown, from the 

 disturbance which would be thereby involved in the general 

 construction of the head, the ridges are attenuated and 

 elongated vertically, either with no increase or in an undue 



VOL. II. L 



