PLATE CXLII 



Type Skull of Menodus varians 



Plate prepared under the direction of Professor Marsh. One-fourth natural size. (See p. 536) 



Menodus (Menops) varians Marsh, type (Yale Mus. 12060), South Dakota, Chadron formation. This skull is referred to Menodus 

 on the following grounds: It is dolichocephalic, with little zygomatic expansion; the incisors are reduced or vestigial; the 

 canines are conical and cingulate; the cheek teeth are elongate anteroposteriorly, and the premolars and molars have the 

 chief characters described above (PI. CXXXIII) ; the nasals are long and distally broad, and the horns are trihedral at the 

 base; the dental and other measurements in general agree with those of Menodus giganteus. Noteworthj' features of the den- 

 tition are the presence of an accessory cusp behind the postero-internal cusp of p'' (a rare or unique character); the great size 

 and depth of the medifossettes of the premolars; the advanced development of the protostyles of the molars; the quadrate 

 character of m'', which has the weU-developed hypocone surrounded posteriorly by a broad cingulum. These characters, 

 together with the thickened tips of the horns, the greater width of the skull, and the widened base of the nasals, appear to 

 indicate a mutation or species distinct from the typical M. giganteus {"ingens"). From Allops crassicornis (see PI. CXX) the 

 present form is distinguished by its more pronounced dolichocephalic characters, especially in the dentition. 



