SYNOPSIS OF THE VEBTEBR^VTE FAUNA OF THE PUERCO SERIES. 307 



Measurements. 



No. 2. Inch. 



r anteroposterior 1.13 



Diameters of vertebral bone ■! transverse 1.20 



I. vertical 40 



This is the oldest species which can be icferred to this genus. 



■! .MAKSUPIALIA. 



All of the Puerco implacentals belong to the suborder Multituberculata, and to 

 three families, which are dclincd a>J follows :* 



Premolars present, compressed and trenchant in form Phir/iaulaeida. 



Premolars present, molariform, dillerent from true molars in form Chirogida. 



Premolars wanting or rudimental Polymasiodontida:. 



To the first belong, in the Puerco fauna, Ptilodus and Neoplagiaulax ; to the 

 second, Chirox ; and to the third, Polymastodon. 



NEOPLAGIAULAX Leinoine. 

 Bulletin of the Geological Society of France, 1881, November. 



I have referred the American species of PlagiaulacidsTi with but one, the first 

 inferior premolar, to the above genus. Those with two premolars I have referred to 

 Ptilodus (October, 1881). 



Neoplagiaula.\ molestus Cope ; Amer. Naturalist, 1886, p. 4.51. 



This species was establi.shed on a separate first inferior premolar. T now 

 describe a mandibular ramus whicii probably belongs to it. It has sullered the loss 

 of the crown of the molar, and the greater pan of that of the i)remolar teeth. The 

 latter has its base oblique in both the vertical and horizontal directions ; its posterior 

 base rounded. True molars small, and on the inner side of the coronoid process. 

 Incisor one, rodent-like. Angular infiection of the mandible well developed, but the 

 posterior bordei- has 1)een broken away. Its form is lobust, especially at the exteiiial 

 base of the large premolar tooth, where a longitudinal swelling rises posteriorly, and 

 disa])pears in the base of the coronoid process. Below and posterior to this protuber- 

 ance the mas.seter fossa extends, having an oblique boundary below in the externo- 

 superior face of the external infiection of the base of the ramus. The internal infiec- 

 tion commences more posteriorly, and projects inwards at a right angle to the vertical 

 plane. Anterior to these infiections the inferior outline of* the i-amus is gently con- 

 vex downwards in conformity to the arc required by the alveolus of the hu-ge 



*Amer. Natunilist, 18S4, p. 687 ; 1887, p. !;07. 



