Marsh Collection^ Peabody Museum. 363 



molar. Farts of the alveoli for all the remaiDing teeth in front 

 are also recognizable, so that the number of the teeth can be 

 accurately determined. With this I associate three other speci- 

 mens, in two of which the last molar is well preserved. 



The jaw has about the same depth as that of the larger 

 species of Microsyojps^ which it otherwise resembles in its 

 general form. The symphysis is deep and rugose, projecting 

 somewhat below the level of the lower border of the ramus, 

 but exhibits no traces of coosification. The alveolus of the 

 enlarged incisor lies close to the symphysis, and unlike that of 

 Microsyojps indicates an almost vertical position for this tooth. 

 Immediately behind the incisive ^^^^ 



alveolus is a medium-sized socket 

 for the first premolar or canine. 

 Behind this comes a two-rooted 

 tooth, with the larger of the roots 

 posterior. The third premolar is 

 likewise two-rooted. A portion of 

 the crown denotes that there was a 

 slight indication of a heel. The ,. ^i^-y^^ 118. -Anterior por- 



^ x- i-i '11 tion of lower law (type or Hyop- 



rest of the crown is broken away. ,^^,,, ^,.^,.^,.^ ^J^^^ ^^^ ^j^^t 



The fourth premolar is in about the lower molar of Smilodectes gra- 

 same stage of evolution as that of ^/Zis Marsh ; side view of jaw, 



Lin^notAeriumormtharotm. The ^^ ZZxT^:",.^^ 

 mternal cusp, however, is smaller, 



but the heel is broader and provided with two cusps instead of 

 one. The first molar also closely resembles that of Limnothei'iuTn 

 tyr annus ^ lacking the great transverse breadth of the posterior 

 part of the crown seen in Microsyops. The arrangement of 

 the cusps is very similar to that seen in Limnotheriwtn. 



I also place in this species three specimens in which the last 

 lower molar is preserved, but which do not show the number 

 of teeth. The association may be therefore incorrect. In one 

 specimen, part of an upper molar is preserved which exhibits 

 a structure like that of Microsyops, and not like that of Lim- 

 notherium. The last lower molar, on the other hand, resem- 

 bles the same tooth in Limnotheriimi more than that of 

 Microsyops^ from all of which, in connection with the charac- 

 ters of the type, I conclude that the specimens must be referred 

 to the species under consideration. 



The last molar differs from that of Microsyops in the central 

 position of the posterior cusps. In Microsyops^ as we have 

 already seen, this cusp stands almost directly behind the inter- 

 nal one. In this respect the tooth resembles the last molar of 

 Limnotherium^ but the cusp is not so large and is more dis- 

 tinct from the posterior rim of the heel. Again this molar 

 differs from that of Limnotheriuin in having a distinct internal 



