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December 19, 1849. 

 The President in the Chair. 

 Present, forty members and gentlemen by invitation. 



The President presented to the Society a cast of a cranium 

 of a young Mastodon. He pointed out the distinguishing 

 features indicating its age. The principal of these was the 

 number of tubercles belonging to the teeth. The animal 

 had passed its earliest period, as was shown by the absence 

 of the first and second teeth, which had been shed. The 

 original cranium was obtained in New Jersey. 



Prof. Agassiz said he would avail himself of the juxtapo- 

 sition of the Mastodon cranium and the skeleton of the 

 Manatee recently presented, to point out some points of 

 resemblance between them. 



The Manatee, he said, has been improperly considered a Cet- 

 acean. It differs from these in the form of the skull, which 

 is elongated, and in the position of the nostrils, which are in 

 front. On the other hand the skull resembles that of the ele- 

 phant in form, particularly when seen from above, in some of 

 the details of the facial bones, as in the zygomatic arches, which 

 are unlike those of Cetacea, in the palatine bones and the 

 arrangement of the teeth, and in the curve of the lower jaw. 

 Blainville has hinted that Cuvier's order Cetacea includes two 

 distinct types of animals. Prof. Agassiz said he would add that 

 he believed the Manatee to be the true embryonic type of the 

 Pachyderms. 



Prof. Agassiz said, that having pointed out to the Society, 

 at a previous meeting, the difference of type in the circu- 

 lating system of different classes of animals, he now pro- 

 posed to demonstrate a similar difference in the respiratory 

 system. 



It was unphilosophical, he said, to speak of the organs of res- 

 piration as only of two kinds, lungs and gills. Among the 



PROCEEDINGS B. S. N. H. 14 MAY, 1850. 



