SYNOPSIS OF THE VERTEBRATE FAUNA OF THE PUERCO SERIES. 351 



ANISONCHUS Cope. 



Proc. Amer. Phil. Soc, 1881, p. 488 ; Tertiary Vcrtehrata, 18S5. p. 408. 



Aniso.\ciiu3 mandibularis Cope: Amcr. Naturalist, 1881, p. 831. Mioclwnus jnandibularis Cope; Tertiarj' Vcrtc- 

 brata, 188.">, p. 339. 



The discovery of a second specimen of this species, wliich inchides nearly all of 

 the dentition of both jaws, i)roves that the position I originally assigned it is the 

 con-ectone. The second superior premolar is like the first in having an internal cusp, 

 whose base is, like that of the A. sectorius, concentric with the principal cusp of the 

 crown. 



The great peculiarity of the species, which is displayed by all the specimens, is 

 the relatively large size of the second inferior premolar. It exceeds the first in ante- 

 roposterior extent, which is in turn longer than any of the true molars. The third 

 premolar is also shorter than the second. '^Phe fourth premolar and canine are not 

 preserved. The fifth cusp is well developed on the first and second true molars, but 

 is of reduced proportions on the third. The heel supports the two lateral and smaller 

 median cusps usual in tlris group. On the third molar the laterals are compressed and 

 the median has a posterior position. 



In the superior true molars the second exterior cus]) of the third is well developed. 

 The fourth cusp is situated well inward.s, furtlici- th;iu in A. sectorius, but not so far 

 as in A. conifencs. There is a short anterior cingulum, which disappears before 

 reaching the internal angle of the crown. External cingulum distinct. The second 

 premolar is as large as the first, and both have a small .inti lior l>asal t iibci-fic. En- 

 amel surface smooth. Thiid incinolar of irdnced diameters. 



ileasurementa. jV. 



Length of six superior molars. . '. 0:!li 



" " true molar series 010 



( anteroposlcrior 00G5 



Diameters p. m. ii ■; „„_ 



> transverse ""' 



anteroposterior "OO 



Diameters p. m. ii 



Diameters m. ii ^ ... 



' transverse "" 



Length of posterior five inferior molars •''-" 



inferior true molars ""' 



I anteroposterior ""8 



' transverse itOiWTt 



Length of p. m . i ^'' 



^ ( anteroposterior « ^•' 



Diameters m. i < noio 



I transverse ""'- 



A. P. S. — VOL. XVI. 2s. 



