No. 2.] COPE ON PERMIAN BATRACHIA AND REPTILIA. 81 



There are tbree teetli in eacli preraaxillary bone. In the maxillary 

 I count seventeen, with the bare possibility of a necessity for adding 

 one more. The first premaxillary and third maxillary teeth are of nearly 

 equal size and are much larger than the others, the second premaxillary 

 only approaching them. The section of the base of the first premaxil- 

 lary is subtrifoliate, there being one grove on the inner, and two on the 

 external face. The section of the middle of the crown is more than a 

 semicircle, with the base convex. The two angles are the sections of two 

 ridges which are both presented posteriorly, the one on the inner the 

 other on the external face of the crown. The crown of the second pre- 

 maxillary has the same form, but the base has only slight traces of the 

 grooves. The third premaxillary is a diminutive of the second. 



The crowns of the maxillary teeth differ from those of the premaxil- 

 laries in the opposition of the cutting edges, which present anteriorly and 

 liosteriorly. The external face is more convex than the internal. The 

 crown of the large third tooth is not expanded above the root, but its 

 antero-posterior diameter contracts regularly to the apex. The crowns 

 of the other teeth are wider at the base antero-posteriorly than the 

 root. They are all slightly curved backwards, and their edges are more 

 or less regularly crenate. 



Several peculiarities distinguish this species from the D. incisivus, 

 with which it agrees in size. In the first place, the section of the root, 

 at and below the base of the crown of the third or large maxillary tooth 

 and of the seventh tooth posterior to it, is of the form of a figure oc 

 directed antero-posteriorly. This is due to the deep grooving of the 

 tooth on the opposite sides at this point ; the grooves not extending on 

 the crown. The grooves are deeper on the smaller teeth, giving it an 

 almost biradiculate character. In JD. incisivus the sections of these 

 teeth are subquadrate. 



In the second place, the section of the base of the first incisor differs 

 from that in D. incisivus, where it is subquadrate with two subopposite 

 shallow grooves. Next, the nostril excavates the border of the maxil- 

 lary bone ; in B. incisivus, the nostril is separated from that bone by 

 the intervention of the nasal. In that species there are but two pre- 

 maxillary teeth ; in D. semiradicatus, there are three. The teeth which 

 accomjiany specimens of D. cruciger have the same form and propor- 

 tions as those of the JO. incisivus. 



Measurements. 



M. 



Length of dental series '-^"^ 



Lengtli of premaxillary series (and bone) 0-19 



Length of diastema *^^ 



Length of first i:*emaxillary tooth from alveolar border 057 



■^. ,. . .,, , , , , T (anteroposterior 022 



Diameter 01 hrst premaxillary tooth at alveolar bortler^ ^^.^ 



Length of third maxillary from alveolar border 067 



^. ^ ^ ,. 1 .„ , , , , (anteroposterior 020 



Diameter of third maxillary at alveolar border < , , 01^- 



() G B 



