258 PROCEEDIjSrGS OF THE GEOLOGICAL SOCIETY. 



these were based, for the most part, on such obviously trivial cha- 

 racters that discredit was reflected on the species which had a better 

 foundation. 



In 1847, I proposed the name of E. antiquus for molars which are 

 met with in vast abundance in certain of the newer Tertiary beds 

 in England, and in corresponding deposits on the Continent, more 

 especially in Italy ; but no descriptions having accompanied the 

 pubhshed figures, the species has hardly been noticed, and nowhere 

 admitted, by other palaeontologists. 



II. The Stjbgeneea of Elephas. 



In the first part of this essay it was attempted to be shown that 

 the species of Mastodon, with the single exception of M. Sivcdensis, 

 are susceptible of being arranged in two natural groups, TrilojjJiodon 

 and Tetraloi^hodon, according to a definite and isomerous numerical 

 expression of the crown-ridges of the three " intermediate molars " 

 of both jaws, and that this formula implies the ridge-characters of 

 the other molar teeth. 



In the Elephants, the divisions of the crowns of any one of the 

 " intermediate molars " are never less than six ; and in the species, 

 fossil and recent, that are furthest removed from Mastodon in affinity, 

 they range as high as 16 or 18 in the penultimate true molar, or 

 third of the " intermediate " series. They are not isomerous, as in 

 the Mastodons, but deviate from the numerical symmetry either by 

 an augmentation of one ridge to the crown of the last " intermediate 

 molar," constituting the hypisomerous forms, or they are more nu- 

 merous, and augment by progressive increments corresponding with 

 the increase of age, including the anisomerous forms. 



The Elephants with hypisomerous-ridged molars are divisible into 

 the two natural groups, Stegodon and Loxodon; the anisomerous 

 species form a third natural group, for which, as already explained, 

 the term Eueleplias is proposed. 



III. Chaeacters of the Stegodons. 



1. General Remarlcs — The Stegodons form the nearest approach 

 in natural affinity to the Mastodons, and more especially to 

 that subdivision of the section TetralopJiodon which comprises M. 

 {Tetraloph.) longirostris and M. {Tetralopli.) latidens. This is evinced 

 by the low elevation and transverse direction of the crown-ridges, 

 by their nearly uniform height throughout the length of the crown, 

 by their thick enamel, and by the mammiUary form of the ridge- 

 processes. A fragment of one of these teeth, denuded of its coat of 

 cement, and seen by a naturalist for the first time, would at once be 

 referred to Mastodon rather than to Eleplias ; and it was this broad 

 resemblance which struck CHft so forcibly that he applied to them 

 the designation, at the time very appropriate, of Mastodon elephan- 

 toides. But when the essential characters are analyzed, the species 

 are seen to partake more of the nature of true Elephants, — 



1st. In the greater number of the crown-ridges and of the mam- 

 milla3 or points that enter into the composition of each. 2nd. In 



