10 



PROCEEDINGS OP THE NATIONAL MUSEUM 



VOL. 77 



Measurements of ramus 



Mm. 



Greatest length of ramus 360 



Greatest depth through coronoid 121 



Greatest depth of dentary at center 87 



Greatest depth of dentary at symphys s 17 



Length of dentigerous border 140 



Teeth. — Four teeth are preserved, three in the left maxillary and 



one in the right dentary. The tooth illustrated (fig. 4) is the fifth 



enumerated from the posterior end of the maxillary, while the germ 



tooth shown in Figure 5 is the twelfth of this 



AV/</W^TIirifll same series. These teeth are retained in their 



illlil ' I' I respective alveoli in such a manner that only their 



t ijjf f // ' ' 1 'VlfvA internal surfaces are visible and for that reason 



fs l^w can not be completely compared with the teeth 



^^^j^^tiMlmij of other described forms. The functional tooth 



\ "^''ilji consists of a laterally compressed crown and evi- 



_ ' „ dently a long cylindrical root. The crown is 



Figure 4. — Maxillae'? *^ i i 



TOOTH OF palaeos- swolleu at the base with a roughened cmgulum as 

 ciNCDs KUGosiDENs. gj^^^j^ ^^ Figurc 4. It Is to this roughening of 



Type. No. 11868, = . 



u.s.N.M. INTERNAL the lowcr part of the crown that the specific 

 VIEW. TWO AND ONE- jjg^j^g Tuoosidens refers. The anterior and poste- 



HALF TIMES NAT- ^ ^ ^ _ ^ 



URAL SIZE rior margins of the crown are denticulate, there 



being three denticles posterior and four anterior to the apical den- 

 ticle, making eight in all. The three central denticles, which in this 

 tooth are missing, appear to have been united as they are in the 

 typical PalaeoscincMS costatus tooth (fig. 3, pi. 4). The other denti- 

 cles are sharp pointed and continue down the inner face of the 

 crown as low, well-defined ridges. The germ tooth has 

 seven denticles, all displaying distinct points, as shown 

 in Figure 5. The apical denticle is slightly posterior 

 to the central vertical line. The anterior teeth, judg- figure 5.— 

 ing from the relative sizes of the alveoli, are smaller ?^^,\^°J 



O ' GERM MAXIL- 



than the posterior. lary tooth 



In relative size, the one functional tooth present °^ palaeos- 



' _ '■ CINCUS RUGO- 



agrees almost precisely with the type tooth of Palae- sidens.typb. 

 osdncus costatus. 'They also agree in having a similar ^ g^^ m'^^in- 

 number of denticles with the median ones closely ternalview. 

 united. On the other hand their successive arrange- JiTe^hIlp 

 ment differs, and whereas P. rugosidens has the lower times nat- 

 part of the crown ornamented with a rugose crinkling ^^^^ ^^™ 

 of the surface, the crown surface in P. costatus is always smooth. 



In the paleontological collections of the United States National 

 Museum there are between 50 and 60 teeth from the Judith River 

 beds of Montana, that with a few exceptions are of similar pattern 



