342 SYNOPSIS OP THE VERTETJRATB FAUNA OF THE rUERCO SERIES. 



Measurements No. 1. ^• 



f anteroposterior """*' 



Diameters m. i \ nn'iT 



I transverse uu.j.j 



f anteroposterior 003 



Diameters m. iii - (\(\'-.k 



I transverse uu.j.) 



No. 3. 



Length of premolar scries 02G 



Depth of ramus at m. i ^^^ 



' p. m. iv 008 



All the specimens of this species are from the Upper Puerco. 



ClIIUACUS INVERSUS sp. nov. 



The characters of this species are so well marked that I introduce it here, 

 although the material representing it is slight, a portion of a single mandibular ramus 

 which supports three premolars, and one true molar. The posterior part of a ramus 

 accompanies this specimen and may belong to the same species. But of this there is 

 doubt. 



The first premolar has a well-developed interior cusp, and a large heel. The lat- 

 ter has an internal vertical, and an external oblique side, terminating in a cutting 

 edge, the internal curving round the posterior border to meet the external. There is 

 no anterior basal cusp, nor any cingulum. The second and third premolars are com- 

 pi-essed, and have cutting edges before and behind. The second has the heel slightly 

 transverse, and a mere trace of anterior basal lobe. Tbe third is larger than the sec- 

 ond and is more compressed. Externally its face is regularly convex, but internally 

 its convexity is a vertical median rib, and in front of this the face is concave, thus 

 maintaining the acuteness of the anterior cutting edge on wear. The heel is small 

 and comjiressed ; anterior lobe none. The enamel of all the teeth is smooth. No 

 cingula. 



3Icnsurcmenls. M. 



Length of posterior tlueo jtrcmolars 015 



" " p.m. iv 007 



Width " •■ " 0038 



Depth of ramus at front of m. i 0115 



TRiiSODON Cope. 



Amer. Naturalist, 1881, p. 007 ; Tertiary Vertchrata, 1885, p. 270. 



But one species of this genus is described, although several have been referred 

 to it. All but the type species have found a congenial location in the genus Mio- 

 cla3nus (group Goniacodon). I am now able, however, to add a second species of 

 ty])ical form. 



