1885.] NATURAL SCIENCES OF PHILADELPHIA. 51 



inwardly of the latter. Regarding it as a first upper molar, 

 it is twice the breadth of the corresponding tooth of 

 Mylodon robustus, not only absolutely, but also proportion- 

 ately in comparison with all the other teeth, except the last 

 one of the lower series. The triturating extremity is worn away 

 obliquely and concavely behind for about two-thirds the breadth 

 of the tooth, and obliquely in front the remaining third of the 

 breadth, but the slopes extend only half the depth observed in 

 the accompanying specimen of the first lower molar. In view of 

 the dentition of Mylodon robustus, it seems improbable that this 

 tooth should belong to an animal of the same genus, nor would it 

 appear to be adapted as an opponent to the comparatively 

 narrow, long-pointed tooth which accompanies it. Nevertheless, 

 he was suspicious that both these teeth may pertain to the 

 Mylodon Harlani, partly from the fact that the lower-jaw 

 fragment, originally referred to Orycterotherium missouriense, 

 and then to the latter, contains a first molar like the Louisiana 

 specimen, and partly from the fact that the jaw-fragment was 

 accompanied by an isolated molar tooth nearly resembling the 

 supposed upper first molar from Louisiana. A plaster cast of 

 the tooth referred to Orycterotherium, of which the triturating 

 extremity and transverse section are represented in the outlines 

 5 and 6, though rather smaller, is sufficiently like the corres- 

 ponding Louisiana tooth to render it probable this belonged to 

 the same animal. Admitting that the two Louisiana specimens 

 may not belong to the reputed Mylodon Earlani, he felt that the 

 coincidence of facts is such as not to justify a conclusion to refer 

 them to a new genus, and if further discovery should demon- 

 strate that they really pertain to this animal, it becomes a 

 question whether the difference of the teeth from those of Mylodon 

 robustus is not sufficient to restore the name of Orycterotherium, 

 missouriense. 



Fig. 1. Outer view of the first lower molar; Louisiana speci- 

 men ; length, 85 mm. Fig. 2. Transverse section ; the front 

 above, the outer side to the right ; fore and aft, 24 mm. ; short 

 diameter, IT mm. Fig. 3. Outer view of the first upper molar, 

 Louisiana specimen ; length, 83 mm. Fig. 4. Transverse sec- 

 tion ; fore and aft, 34 mm.; short diameter, 19 mm. Fig. 5. 

 Outer view of cast referred to Orycterotherium ; length, 67 mm. 

 Fig. 6. Transverse section; fore and aft, 29 mm. ; short diameter, 

 17 mm. 



The following were ordered to be printed : — 



