Marsh Collection, Peabody Museum. 345 



The first molar, or sectorial, bears the unmistakable stamp 

 of an early or primitive condition of this tooth in the Car- 

 nassidentia. This is particularly noticeable in the great 

 elevation of the trigon above the heel, in the large size of the 

 internal cusp and the arrangement of the cusps of the trigon 

 in the form of an isosceles triangle, in the obliquity of the 

 principal shear to the axis of the jaw, and the development of 

 a posterior shear. In the sectorial of Cynodictis or of a modern 

 dog, the trigon is less elevated, the principal shear is more in 



Figure 2. — Left lower jaw Vulpavus Hargeri Wortman ; crown view ; one and 

 one-half natural size. (Type.) 



line with the jaw axis, the internal cusp of the trigon is 

 reduced, and the posterior shear has practically disappeared. 

 Of the trigon the external or principal cusp is unusually high 

 and prominent ; it has a distinctly trihedral form, with the 

 anterior cutting edge but little produced, in marked contrast 

 with that of Cynodictis or the fox, in which the whole cusp is 

 laterally flattened and the anterior edge drawn out into a 

 cutting blade. The anterior cusp is prominent and relatively 

 thick ; its posterior edge is extended and forms the more 

 important blade of the principal shear. The internal cusp is 

 large and with the principal outer cusp forms a posterior, 

 transverse shear of considerable efficiency, which bites against 

 the anterior edge of the first superior molar. The heel or 

 talon is proportionally small ; it is made up of an inner basin- 

 shaped and an outer vertically beveled part, divided from each 

 other by an antero-posterior median ridge, which is terminated 

 behind by a rounded cusp and continued forwards to the base of 

 the trigon. The inner boundary of the basin is furnished by a 

 ridge of moderate proportions which curves around posteriorly 

 to join the median cusp, inclosing between it and the median 

 ridge a concavity. The antero-posterior ridge joins the base 

 of the trigon immediately posterior to and beneath the notch 

 which separates the blades of the posterior or transverse shear. 

 The extent to which this outer beveled portion of the heel is 

 developed varies much in the different species of Canidae ; it 

 has to do apparently with the pushing inwards of the principal 

 external cusps of the first superior molar, for when they have 



