234 Btdletin American Museum of Natural History. [Vol. XIII, 



I. Lower Oligocene. Incert^ Sedis. 



Ronzoti, Argiles du Cantal, Phosphorites, Cadi bona. 



A most interesting primitive Lower Oligocene type is : 

 Ronzotherium gaudryi ^(Zw^j-. Type: a lower jaw, Paris Museum. Local- 

 ity, Brons, Cantal. Definition : dentition -g- -j- -3- -3-- ; second pair of lower in- 

 cisors greatly reduced ; median or first pair typical ; lower canines erect, laterally 

 compressed ; first lower premolars wanting ; premolars 3-4 with internal and ex- 

 ternal cingulum ; molars 2-3 without internal cingulum ; premolars 2-4 much 

 worn but apparently simple in pattern, i.e., without complete posterior crests. 



Systematic Position. — The ^r^r/ lower canines indicate the ex- 

 istence of upper canines, as in the Amynodontidae or in Leptacer- 

 athcrium trigonodum Osborn ; the laterally compressed shape of 

 the canines resembles that in Leptaceratherium and is distinct from 

 the more triangular form seen in At/iynodon, but, if a member 

 of the Rhinocerotidse, this animal was very primitive. Since it is 

 certainly not a member of the genus Aceratherium it may be pro- 

 visionally referred to the genus Ronzotherium Aymard, the type 

 of which is a lower jaw from Ronzon, similar in some respects. 

 The absence of the first lower premolar in R.gaudryi and R. ve- 

 launum is also distinctive of the Diceratheriinge. 



According to M. Boule the Argiles du Cantal, containing R. 

 gaudryi, are, if anything, a shade older than the Marnes de Ron- 

 zon, containing R. velaunum. 



The jaw is slightly smaller than that of R. velaunum,^ there is 

 a wider space behind the third molar ; the dentition is similar in 

 the simplicity of the premolar teeth ; in fact it may subsequently 

 prove that R. velaunum and R. gaudryi are allied. 



Space occupied by lower 1 r, ^1 ■ , ■ 



^ r y Ronzotherium gatidryi 170 mm. 



grinding series, premolar > , . , ,. „ ., • ; 



" . . {^'iiwas.i&o.) Ronzotneriiun vela uii ujii .. .i()^ mm. 



2 to molar 3 inclusive I 



The lower grinding series of R.gaudryi \?, closely equal in size 

 to that of the Upper Oligocene D. niinutum series (p2-m3 = 

 173) in the Paris Museum. 



Ronzotherium velaunum Aymard. — Type : A lower jaw. 

 Collection Aymard, Puy Museum. The writer has not personally 

 examined the type and must rely upon the descriptions and figures 



> M. Filhol gives no measurements but figures the jaw of R. velaunum as | natural size 

 (Plate xii, figure 69, pp. 75, 266, Mammiferes Fossiles de Ronzon). 



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