EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHERES 



407 



Measurements of Dolichorhinus longiceps and D. hyognalhus, in 

 millimeters 



Tip of nasals to occipital crest 



(lateral) 



Premaxillary to condyle 



Transverse zygomata 



Face, anteroposterior (premaxil- 

 lary tp postorbital process, 



frontal) 



Cranium, anteroposterior (post- 

 orbital frontal to condyle) 



Pi-m3 



Pi-p< 



M'-mS 



P', ap. by tr 



P^ ap. bytr 



M', ap. by tr 



M2, ap. by tr 



M', ap. by tr 



D. longi- 

 ceps, Car- 

 negie Mus. 

 2347 (type) 



590 

 '555 

 264 



"270 



■■285 



197 



79 



115 



15X11 



21X29 



35X ? 



39X40 



39X ? 



D. hyognnttius 



Am. Mus 

 1852 (a 



transitional 

 form) 



'550 

 230 



270 



283 



202 



78 



118 



20X26 

 36X33 

 41X39 

 40X37 



Am. Mus. 

 1851 (typo 



of Tel- 

 matotlie- 



rirua 

 cornutum) 



577 

 550 

 '240 



280 



288 



208 



82 



122 



15X10 



23X27 



34X34 



43X43 



45X45 



Thus these measurements indicate that as com- 

 pared with the type of T. cornutum { = D. Jiyognathus) 

 the type of D. longiceps is somewhat broader and its 

 tooth dimensions sUghtly less, except that p** is wider. 



Field Museum sJculls. — The four skulls as described 

 by Riggs (1912.1, p. 33) are somewhat smaller, less 



specialized than the type, and range in length from 

 525 to 560 millimeters. One of the largest, a finely 

 preserved skull, is shown in Plate LXXVI. There is 

 little evidence of incipient horn cores. The nasals 

 overhang the margins of the premaxillaries, which are 

 somewhat narrower than in the type of Douglass. 

 Compared with the type of D. intermedins, the smaller 

 D. longiceps skull (Field Mus. 12193) approaches 

 closely in size; the dental series is similar in length; 

 the premolars are more advanced in structure. In 

 the palate there is a ridge between m^ and m^ corre- 

 sponding to the primitive position of the posterior 

 narial border, which is bridged over by the outgrowth 

 of thinner plates from the lateral margin of the palatal 

 bones so that the nares have receded to a point behind 

 the hamular processes of the pterygoids; the plates 

 of this secondary palate are, however, so thin that 

 they are often broken through, so that the secondary 

 border of the posterior nares can not be precisely 

 determined. The secondary palate in this species is 

 pierced by a pair of foramina; its posterior extension 

 is an enfoliate process free from the lateral walls and 

 probably attached to the inferior margins of the vomer 

 (Riggs). 



A mandible associated with the incomplete skull of 

 D. longiceps (Field Mus. 12200) is relatively strong, 

 curved in the ramus, and broad at the angle. The 

 skeleton of this same specimen, which was found near 

 the base of Uinta B 1, is described on page 651. 



The detailed measurements of these skulls are given 

 in the following table: 



Measurements of DolicJiorJiinus iy Riggs, in millimeters 



D. longi- 

 ceps, Car- 

 negie Mus. 

 2347 (type) 



D. cornu- 

 tus. Field 

 Mus. 12167 



D. flumi- 



nalis, Field 



Mus. 12205 



(type) 



Skull: 



Length, incisors to condyles 



Breadth across arches 



Breadth above orbits ; 



Postorbital process to condyles 



Last molar to condyles 



Length of free nasals 



Greatest breadth of nasals 



Postglenoids to condyles (median line) . 



Length of molar-premolar series 



Length of molar series 



Length of crown of canine 



Diameter of crown of canine 



Length of diastema 



Narrowest point in sagittal area 



Breadth of orbitonasal area 



Mandible: 



Length, condyles to incisors 



Height, condyles above angle 



Length of molar-premolar series 



Length of molar series 



Length of crown of canine 



Diameter of crown of canine 



Depth of ramus from base of ps 



Depth of ramus froiia base of ma 



'545 

 260 



595 

 285 



'310 



300 



152 

 81 



197 

 115 



140 



214 



135 



40 



22 



16 



550 



247 



'134 



305 



263 



170 



79 



122 



212 



131 



24 



17 



14 



52 



'560 

 255 

 130 

 305 

 280 

 160 



530 

 240 



'535 



295 

 258 



132 

 264 

 259 



520 

 233 

 116 



137 

 57 



121 

 200 

 124 



115 

 192 

 121 



67 



114 

 198 

 122 



171 



105 



32 



18 



400 



159 



209 



123 



29 



16 



70 



57 



» Estimated. 



101959— 29— VOL 1- 



