NATURAL SCIENCES OF PHILADELPHIA. 



99 



the corresponding tooth of the American Mastodon, but is considerably 

 smaller. It bears sufficient resemblance to the plaster cast (represented in 

 fig. 14, pi. xxvii., of " The Extinct Mammalian Fauna of Dakota and Ne- 

 braska, &c,") of a tooth, the original of which is lost, from a miocene forma- 

 tion of Maryland, to be viewed as pertaining to the same species. This I had 

 named Mastodon obscurus. 



The crown of the tooth consists of four transverse divisions together with 

 the merest trace of a heel. As in the cast of the Maryland tooth, the inner 

 lobes of the crown of the California tooth are more mammillary, and less 

 angular than in M. Americanos. The outer lobes, likewise as in the Maryland 

 tooth, have better developed offsets fore and aft internally than in the latter, 

 giving rise to a greater degree of obstruction of the transverse vallies of the 

 crown than in the American Mastodon. The fourth division of the crown is 

 proportionately less well developed, in comparison with those in advance, 

 than in the latter, agreeing also in this respect with the Maryland tooth. The 

 outer lobe of this division is formed of a pair of connate mammillary tuber- 

 cles, as in the latter, but the tubercles are more equally developed. The in- 

 ner lobe is a single mammillary eminence not more than half the elevation 

 of the outer lobe. In the Maryland tooth, the corresponding lobe resembles 

 the outer one, consisting of a connate pair of tubercles as well developed as 

 in the outer lobe. The heel in the California tooth, as in the Maryland tooth, 

 is formed by a short mammillary eminence occupying the angular space pos- 

 teriorly of'the lobes of the fourth division of the crown. A basal ridge 

 is better developed externallv in the California than in the Maryland tooth. _ 

 Comparative measurements of the California tooth, with the cast of the 

 Maryland tooth, and one of the Mastodon americanus are as follows : 



California 

 tooth. 



4 lines. 

 9 lines. 

 2 lines. 



Maryland 

 tooth. 



in. 

 in. 

 in. 



4 lines.* 

 9 lines. 

 2 lines. 



Mastodon 

 americanus. 



in. 3 lines. 

 in. 4 lines. 



in. lines. 



Fore and aft diameter of the 

 crown of the last molar toothJ6 in 



Transverse diameter of do 2 in 



Depth of do. internally 12 in 



It is not improbable that the California tooth may have pertained to the 

 same species as the fragment of tusk previously aoticed, and, perhaps these, 

 together with the Maryland tooth, and others previously referred to Mastodon 

 obscurus may likewise belong to the same animal. The positive determina- 

 tion of this question must be left for the discovery of additional material to 

 throw light on the relationship of the different specimens which have been 

 thus far presented to our notice. 



Sept. 13th. 



The President, Dr. Ruschenberger, in the Chair. 



Twelve members present. 



The following paper was presented for publication : 



" On the flowers of Aralia spinosa and Hedera helix. Uy Inos. 

 Meehan. 



Sept. 20th. 

 The President, Dr. Ruschenberger, in the Chair. 



Twenty-three members present. ^ 



Partially estimated, as the specimen is imperfect at its fore part. 



1870.] 



