174 



of Proboscidians to which he gave the name of Tetracaulodon, in the 

 third volume of the New Series of the ' Transactions of the American 

 Philosophical Society': it has likewise been described and figured by 

 Dr. Isaac Hays in the fourth volume of the same work, plate 26, fig. 1 

 and 2. 



From the tertiary deposits about twelve miles from Newburg, in 

 Orange County, New York. 



Presented by the Geological Society of London. 



713. The symphysis of the lower jaw of a young Mastodon giganteus, showing 



the remains of the alveoli of the two deciduous incisors. 

 From the tertiary deposits of the Ohio, North America. 



Purchased. 



714. A portion of the risjht ramus of the lower jaw of the Mastodon giganteus, 



containing the penultimate and antepenultimate molars of the socket of 

 the last large molar. The crown of the antepenultimate molar supports 

 three transverse ridges, and has an anterior and posterior narrow trans- 

 verse minutely tuberculate talon ; each of the ridges is divided into two 

 maminilloid processes, the innermost of which are the longest ; the 

 crown is supported by two fangs, the anterior one broad but compressed 

 from behind forwards, and with the extremity bifid and bent backwards ; 

 the posterior and thicker fang is deeply grooved on each side. The penul- 

 timate molar has almost the same general form and structure as the pre- 

 ceding, but is of larger size ; there is a small tubercle at the outer end 

 of the bottom of the cavity between each of the transverse ridges : the 

 concavity of the ascending ramus of the jaw displays the upper and lower 

 divisions of the great dental canal, besides the intervening socket of the 

 last molar. 



From the tertiary deposits of Ohio. Purchased. 



715. A portion of the left ramus of the lower jaw of the Mastodon giganteus, 

 including the symphysis and the penultimate and last molar teeth in situ: 

 in the last molar the large posterior talon is developed into a fifth ridge, 

 divided into two mammillary processes and having a small quadritubercu- 

 late talon behind it : part of the three principal fangs are exposed, the 



