318 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [April 8, 



veri 3, deinceps majores, altero alterum extrusum a tergo vicis- 

 sim excipiente, demum utrinque solitarii. — Molares 3 utrinque 

 intermedii (nempe deciduorum postremus et verorum antepe- 

 nultimus penultimusque) colliculis supra 5 (6-18), aut hypi- 

 someris, aut anisomeris. 

 Proboscis longissima, prehensilis. Coi'pus vastum artubus elevatis 

 insistens. Pedes 5-dactyli. 



Subgen. 1. Stegodon. — Dentium molarium 3 utrinque interme- 

 diorum corouis complicata colliculis hypisomeris 

 {e. g. 7+7 + 8), mammillatis, tectiformibus. Prae- 

 molares nondum observati. 



Subgen. 2. Loxodon. — Dent, molar. 3 utrinque intermedior. 

 coronis lamellosa colliculis hypisomeris (e. g.7 -\- 

 7 + 8), cuneiformibus. Prsemolares raro utrinque 2. 



Subgen. 3. Euelephas. — Dent, molar. 3 utrinque intermedior. 

 coronis lamellosa colliculis deinceps numero auctis, 

 anisomeris {e.g. 12+14+18), attenuatis, com- 

 pressis. Prsemolares nuUi. 



Observations. — The adult dentition of the Elephants, although 

 typically more aberrant, is more constant than that of the Mastodons. 

 Inferior incisors are wanting in all the species, fossil and recent, at 

 present known ; and premolars have as yet only been met with in 

 a single form, E, {Loxodon) planifrons. The common formula is, 



Incis. — ; Can. — ; Prcemol. - ; Mol. — = 7 ; but in this exceptional 

 case the premolars are as numerous as in any species of Masto- 

 don, the formula being, Incis. — ; Can. — ; Prcemol.-; Mol.-=\\. 



It exceeds the rest of the species by 8 molars in both jaws, as M. 

 {Triloph.) angustidens exceeds M. {Triloph.) Ohioticus. A longi- 

 tudinal belt of enamel has not yet been observed on the tusk of any 

 Elephant. The molars are presented under two forms : in the sub- 

 genus Stegodon as "Dentes complicati," resembling those of Masto- 

 don in the folded form of their crown-eminences, and as *' Dentes 

 lamellosi" in Loxodon and Euelephas. The convexity of the crown- 

 ridges, and the absence of the longitudinal mesial bipartient cleft, so 

 characteristic of the true Mastodons, are very constant in the Ele- 

 phants, the only exception, limited to the latter character, being in- 

 distinctly seen in an E. {Stegod.) Cli/tii. The passage from the 

 Stegodons into the Loxodons is effected through E. {Steg.) insignis 

 and E. {Loxod.) pla7iifrons ; and from the Loxodons into Euelephas 

 through E. {Lox.) meridionalis and E. {Eiiel.) Hysudricus. The 

 anisomerous ridge-formula in Euelephas is not numerically the same 

 in all the species, being in some higher, in others lower : but they 

 all agree in exhibiting progressive increments. The amount of un- 

 dulation presented by the worn edges of the enamel-plates furnishes 

 a good means of distinguishing the nearly allied fossil species in 

 Euelephas. 



The distinctive and specific characters of Mastodon and Elephas. 

 — A safe criterion by which to test the soundness of any proposed 



