216 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Millimeters 



Expanse of zygomatic arches 558 



Least distance across vertex 157 



Space occupied by four upper premolars 162 



Space occupied by three upper true molars 266 



Space occupied by molar-premolar series 428 



Etymology. — ingens, vast. 



Present determination. — The species is a synonym of 

 Menodus giganteus Pomel. 



Symborodon hypoceras Cope, 1874 

 Cf. Brontotherium hypoceras, this monograph, page 562 



Original reference. — U. S. Geol. and Geog. Survey 

 Terr. Ann. Rept. for 1873 (Hayden), p. 491 [no 

 figure], 1874 (Cope, 1874. 2). 



cores of very different shape described below. (See 

 fig. 174.) 



Specific characters. — Infraorbital foramen "fiat with 

 a wide external face, instead of being a cylindric col- 

 umn as in S. acer, altirostris, bucco, and ophryas." 

 One of the horn cores "consists of the extremital 

 part. * * * j^g section is a compressed oval 

 narrowed in front; its profile with parallel outlines and 

 a little recurved and not very rugose. Its size as 

 compared with the rest of the skull is the smallest in 

 the genus, and not more than half the proportions of 

 the S. altirostris." Another fragment Cope deter- 

 mined as a portion of the frontal bearing a "large 

 osseous tuberosity, which consists of a mass of bone 



FiGTJRE 171. — Type (holotype) skull of Symborodon altirostris 

 Am. Mus. 6350. After Cope, 1874. One-sixth natural size. 



Type locality. — ?Cedar Creek, Logan County, Colo. 

 Type. — Cope writes: 



This species reposes on a fragmentary cranium only, which 

 embraces nasal, maxillary, frontal, malar bones, etc., both 

 zygomata, premolar, and parts of molar teeth. These frag- 

 ments were taken out of the matrix by the writer and were 

 found in juxtaposition. They represent parts of the same 

 skuU and, as no other was found in the same bank, are prob- 

 ably without admixture. 



The only remains representing this type which are 

 now preserved in the American Museum of Natural 

 History (Am. Mus. 6361) include two portions of the 

 malar bones, a fragment of the orbit and infraorbital 

 canal, a fragment of the alveolar region, and two horn 



coossified with the upper surface as in the horn of 

 the girafi'e." Cope concluded that "it is probable 

 that this species possessed two pairs of osseous proc- 

 esses or cores on each side, the one on the nasal, the 

 other on the frontal bone." The name "hypoceras" 

 doubtless referred to the supposed presence of the 

 second horn core (the rounded tuberosity) behind and 

 below the oval-sectioned horn on the nasals. Cope 

 gives 14 measurements, including the following: 



Millimeters 



Length from front of orbit to glenoid fossa (axial) 365 



Depth of malar below orbit 20 



Length of molars and last three premolars 293 



Length of last three premolars 110 



Diameter of horn core, transverse 38 



