444 Geological Society. 



at the mouth of Babbage River, on the coast west of the Mackenzie, 

 containing the species of Cyclas (C. medius) which occurs extensively 

 in the weald-clay of England. 



This memoir, which will be published in full in the Appendix to 

 Captain Franklin's Narrative of the expedition, is illustrated by maps 

 and drawings, and accompanied by a catalogue in detail, of the speci- 

 mens referred to, which have been presented to the Geological Society. 

 April \8. — William Hutton, Esq. of Newcastle-upon-Tyne, Beriah 

 Botfield, Esq. of Christchurch Oxford, and William Parker Hamond, 

 Esq. of St. John's College Cambridge, were elected Fellows of this 

 Society. 



A Paper was read, " On the fossil remains of two new species of 

 Mastodon, and of other vertebrated animals, found on the left bank of 

 the Irawadi j by William Clift, Esq. F.G.S. F.R.S., conservator of the 

 Museum of the Royal College of Surgeons." 



The author having been requested to describe the fossil remains 

 which the zeal and liberality of Mr. Crawfurd have transferred from 

 the deserts of the Irawadi to the Museum of the Geological Society, 

 confines himself strictly to zoological and anatomical details ; and fol- 

 lowing the system of Cuvier, commences with the 



Pachydermata proboscidifera. — The only genus of this order indi- 

 cated by the remains is the Mastodon ; and of this there are two spe- 

 cies, Mastodon latidens and Mastodon elephantoides, not only com- 

 manding attention from their novelty, but from the beautiful gradation 

 which they exhibit between the mastodons already described and the 

 elephant. On comparing the teeth of Mastodon latidens with those 

 of the mastodon of the Ohio (M. giganteum) the denticules are found 

 to be more numerous, and less distant, and the interstices less deep 

 than in those of the latter. The teeth, in short, begin to assume the 

 appearance of those of the elephant. On advancing to Mastodon 

 elephantoides, these features of similarity are more strongly deve- 

 loped : the many-pointed denticules are still more numerous and 

 more compressed j and the structure, were it not for the absence of 

 crusta petrosa, becomes almost that of the tooth of the elephant. 

 In both, though the teeth are formed upon the principle by which 

 the tooth of the mastodon is distinguished from that of the elephant, 

 the crown of the tooth wears away more like that of the elephant t,han 

 that of the other mastodons. 



The species are thus characterized : 



Mastodon latidens. — Mastodon dentibus molaribus latissimis, den- 

 ticulis rotundatis, elevatis. Palato vald& angusto. 



The dentition very much resembles that of the ' elephant. The 

 molar tooth is gradually pushed forward, and rises as the fangs are 

 added, according to the demand occasioned by the abrasion of the ex- 

 posed crown, and the consequent absorption of the anterior fang ; the 

 posterior part of the tooth not having yet cut the gum, while the an- 

 terior portion is completely worn away. Before it are seen the relics 

 of the preceding tooth, the place of which the tooth in use was pro- 

 gressively supplying. 



The lower jaw in this species is less square and deeper than it is in 

 M. tngantcum. 



The 



