936 



EODENTIA 



of brain-case ; paroccipital process robust, not very long, its 

 extremity projecting silghtly beyond level of lower edge of 

 condyle ; basioccipital broad and short, its lateral processes very 

 distinct ; auditory bulla moderately large, evenly inflated, the 

 region below meatus constricted to form a short but evident 

 neck. Interorbital region broad, squarish, the median portion 

 depressed ; postorbital processes heavy, standing out abruptly, 

 not much bent downward, separated from brain-case by a wide 

 space ; orbit about two-thirds surrounded by bone. Nasals 

 abruptly bent downward anteriorly, considerably narrowed 

 posteriorly, so that their combined breadth at level of posterior 

 border of premaxillaries is only a little more than half greatest 

 anterior breadth. Incisive foramina extending back slightly 

 into maxillaries, their outer borders nearly parallel. In other 

 respects the skull so closely resembles that of Citellus citellus, 

 due allowance being made for its greater size and angularity, as 

 to require no detailed description. 



Teeth. — In general form the teeth bear a strong resemblance 

 to those of Citellus citellus. Upper incisor with anterior face 

 slightly flattened, somewhat distorting the otherwise evenly 

 semicircular outline of cross-section, the enamel deep yellowish 



brown, its surface marked by about 

 four faintly indicated longitudinal 

 ridges ; enamel of lower incisor 

 minutely pitted. Enamel pattern 

 of upper cheek-teeth essentially as in 

 Citellus citellus, but inner tubercles 

 lower and less compressed, the length 

 of base slightly greater than height 

 of tubercle, transverse ridges form- 

 ing a V-shaped rather than U-shaped 

 figure when worn, and anterior and 

 posterior ridges continuous at their 

 inner extremities with anterior and 

 posterior bases of inner tubercle. 

 Other details in which the upper 

 cheek-teeth differ from those of C. 

 citellus are as follows : no indication 

 of minute secondary cusps or ridges 

 between main cusps of outer side ; small premolar with 

 crown area barely half that of succeeding tooth, its anterior 

 and posterior depression tending to join on inner side to form 

 a narrow semicircular concavity; depression on posterior half 

 of m 3 flattened rather than basin-shaped. Lower cheek-teeth 

 differing from those of Citellus citellus in their relatively much 

 lower, more robust cusps and larger crushing surfaces, and the 

 relatively greater importance of ridge joining inner bases of 

 outer cusps, this ridge so high that it begins to wear almost as 

 soon as the cusps themselves, forming a conspicuous feature of 



FIO. 193. 

 Marmota marmota. 

 Cheek-teeth. X 2. 



