Cope.] x\J4: [Dee. 16, 



known before the value of this character can be ascertained. If the view 

 that Sarcothraustes has but three inferior premolars be correct, this charac- 

 ter distinguishes it from Mesonyx, as do also tLe transversely expanded 

 heels of the molars. The family Mesonychidce may be for the present re- 

 garded as embracing the three genera of Sarcothraustes, Mesonyx and 

 Dissacus.* 



Char. Specif. The penultimate superior molar has a strong posterior 

 cingulum which commences within the line of the internal bases of the 

 external cusps, and rises into considerable importance behind the internal 

 cusp. There is also an anterior cingulum which does not rise internally, 

 and which is continuous with a strong external basal cingulum. The 

 latter passes round the posterior base of the posterior cone, and runs into 

 the posterior branch of the internal V. The posterior cone is smaller than 

 the anterior cone, and its apex is well separated from the latter. The ap- 

 pearance of this tooth is something like that of a carnivorous marsupial. 



The symphysis mandibuli slopes obliquely forwards, and is united by 

 coarse suture. The ramus is stout and deep, as compared with the size of 

 the molar teeth. The roots of the teeth are relatively large, especially 

 those of the first two premolars. The crown of the canine is lost. The 

 first premolar points forwards, nearly parallel with the canine, and diver- 

 gent from the second premolar. The crown of the second premolar is 

 small and subconic, and has a rudimental heel, and no anterior basal tuber- 

 cle. The first true molar resembles considerably that of Mesonyx. There 

 is a small anterior basal tubercle on the inner side of the principal cusp. 

 The expansion of the heel is transverse only, there being no longitudinal 

 lateral edges or tubercles. The enamel is obsoletely, rather coarsely 

 wrinkled. There are two rather large mental foramina ; the posterior be- 

 low the anterior root of the first true molar, and the anterior below the 

 posterior root of the second premolar. 



Measurements. M. 



Diameters of superior M. ii \ anteroposterior externally .015 



(. transverse 024 



Anteroposterior diameter of base of M. .iii .",". 0095 



Anteroposterior diameter base of crown of inferior 



canine 020 



Length of bases of three inferior premolars 038 



( anteroposterior 019 



Diameters inferior M. i. i transverse ,. . .0095 



( vertical 0110 



Depth of ramus at P-m. iii 0520 



Width " " 022 



* American Natui*alist, Dec., 1881. 



