254 ON THE EXTINCT MAMMALIA OF 



its breadth, which is eleven and a half inches. It contains eighteen and a half 

 rid"-es. of which the widest is four and a half inches. 



9. An inferior molar of the variety referred to Elephas Columbi, from Brunswick 

 Canal Darien, Georgia. It has lost a small portion anteriorly, and is worn its entire 

 breadth, which is eight and three-quarter inches. It contains twelve and a half 

 ridges, and a back heel of cement of about half an inch in thickness. 



Besides the gradual transition of character in the relative thickness of the constitu- 

 ent plates of the molars of the North American Elephant, referred by Falconer to two 

 species, specimens likewise exhibit a gradation in the degree of crimping of the 

 enamel, and also in the mode of wearing, from the more level condition of the tritu- 

 rating surface of such teeth as have been referred to E. prlmicjenius, to the terraced 

 condition viewed as a character of those referred to E. Columbi. 



Since writing the above, I have received for examination from the Smithsonian 

 Institution five Elephant molars, which possess some interest. Four of them are 

 from the Yukon Rivei", Alaska; the remaining specimen is from Petite Ause Salt 

 Mine, Louisiana. 



Of the Yukon specimens, three are much mutilated, and present the ordinary type 

 of structure. The fourth one resembles those referred by Dr. Falconer to Elephas 

 Columbi. It is from an intermediate position in the series, and is probably a third or 

 fourth. It exhibits as great a degree of coarseness of its constituent plates as the sec- 

 tion of the tooth of ^. Columbi, from Georgia, represented in plate 1 of Dr. Falconer's 

 admirable paper on the American Fossil Elephant, published in the Natural History 

 Review for 1862. The back three plates are unworn in the specimen; the anterior 

 five are worn off in the usual manner. The eight plates together at their base occupy 

 a space of six and three-quarter inches; ascending they converge, both from in front 

 and behind, so as to occupy at the triturating surface about a line less than four 

 inches. The back unworn plates are about four and a quarter inches long ; the first 

 worn plate is three inches long. The greatest thickness or width of the tooth, at 

 the middle of the fourth plate, is forty lines. Perhaps these Yukon specimens may 

 belong to Elephas primigenivs. 



The Petite Anse tooth is most decidedly of the character of those referred to E. 

 Columbi. The specimen consists of the greater portion of a much worn last inferior 

 molar. The triturating surface in all its details resembles those of the Elephant 

 teeth from Brunswick Canal, Georgia. 



The fragment of a molar tooth originally referred to a species with the name of 

 Elephas impcrator was obtained by Prof. Hayden on the Loup Fork of the Platte 

 River. I was led to refer it to a species difierent from the more ordinary American 



