NATURAL SCIENCES OF PHILADELPHIA. 417 



Notwithstanding the difference it is easy to see that one form 

 is the derivative of the other, and it is probable that the elephan- 

 tine form was evolved from the inastodont form, as the teeth of 

 the mastodon are of a more ancient pattern or type, that is to say, 

 they accord more nearly with the nsual pattern of the molars of 

 ancient pachyderms. 



By simple multiplication of the transverse lobes of the molar 

 crowns of the mastodon, contracting these lobes, elongating them 

 so as to encroach on the position of the fangs, and filling the 

 intervals with cementum, we have the elephant molars produced. 

 The miocene stegodons of the Himalayas were elephants with 

 teeth decidedly of intermediate character in these respects, with 

 the true elephants and the mastodons. 



This mode of complication of the molar teeth in the evolution 

 of the elephant pattern from the mastodon pattern was a very 

 common one among the ungulates. Most of the early ruminants, 

 as Oreodon, Agriochoerus, etc., and the solipeds, as Anchitherium, 

 had molars with short crowns and prominent lobes, inserted with 

 fangs. Their successors, as exemplified in most living ruminants 

 and the horses, have molars with long crowns, complicated in the 

 same manner as we observe in the elephant as compared with the 

 mastodon. 



Nearl}' all oitr domestic herbivorous ungulates belong to genera 

 having long-crowned, complicated molars, as exemplified in the 

 elephant, horse, camel, ox, sheep, and goat. The deer retains the 

 more ancient pattern of molars. 



That the course of evolution was from the more simple to the 

 more complicated type would appear to be confirmed in the fact 

 that the temporary molars have proportionately shorter crowns 

 and longer roots than in those of the permanent series. 



The death of Prof. Agassiz was announced by the Chair, and a 

 committee consisting of Drs. Le Conte, Carson, and Leidy was 

 appointed to draft resolutions of regret. 



December 23. 



The President, Dr. Ruschenberger, in the chair. 



Thirty-seven members present. 



The following paper was presented for publication : 

 " On Three New Species of Unionidse of the United States." 

 By Isaac Lea. 



Prof. Cope made some remarks on fishes from the coal mea- 

 sures at Linton, Ohio. He stated that Prof. Newberry, Director 

 of the Geological Survey of Ohio, had sent to him numerous 



