84 SINCLAIR— ADDITIONS TO FAUNA OF [April 24. 



referable to Gomphotherium, with a last lower molar carrying four 

 cross-crests and a heel and having the intervening valleys blocked 

 by large accessory tubercles (Fig. 8). A smaller form (Fig. 9), 

 also with four cross-crests and a heel in m^, has the summits of the 

 crests much more acute than in the Gomphotherium type and the 

 valleys as free from accessory tubercles as in the corresponding 

 tooth of Mastodon americanus to which the Snake Creek form is, 

 possibly, related. Accessory ridges occur on the front and rear of 

 the external half of each crest, but are no more strongly developed 

 than in M. americanus. The last lower molar of the latter does 

 not decrease in width posteriorly as rapidly as does the tooth here 

 considered, but in other respects they closely resemble each other. 

 The crown is unworn and there is no trace of cement. 



Fig. 9. fMastodon sp., left last lower molar, two thirds natural size. 

 No. 121 16 Princeton University Geological Museum, collecting locality 1000 A. 



Incert.e Sedis. 



A fragment of the left ramus of a lower jaw. No. 12091 Prince- 

 ton University Geological Museum, collecting locality lOOoA, has 

 not been determined generically (Fig. 10). The specimen shows 

 alveoli for two incisors and part of the root of a third. The first 

 alveolus is very large and shallow and the second narrow and deep. 

 The fragment of the root of the third incisor is strongly compressed 



