134 Zoological Proceedings of Societies, 



designate as the Lagostomus trichodactylus. He also exhibited, and 

 compared it with, skeletons of the Marmot, Urson, Coypus, Isodon, 

 Helamys, Rabbit, Squirrel, and Agouti. 



GEOLOGICAL SOCIETY. 



^pril 18. — A Paper was read. On the Fossil remains of two new spc' 

 cies of Mastodon, and of other vertebrated Animals, found on the left 

 hank of the Irawadi; 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 following the system of 

 Cuvier, commences with the 



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

 cated by the remains is the Mastodon; and of this there are two species: 

 Mastodon latidens and Mastodon elephantoides, not only commanding 

 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 developed : the many-pointed denticules are 

 still more numerous and more compressed; 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 Ele- 

 phant than that of the other Mastodons. 



The species are thus characterized: 



Mastodon latidens. — Mastodon dentibus molaribus latissimis, denticulis 

 rotundatis, elevatis. Palato valde angusto. 



The dentition very much resembles that of the Elephant. The molar 



