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Genus Elasmotherium*. 



923. A cast of the left ramus of the lower jaw, including the symphysis, of 

 the Elasmotherium Fischeri, Cuvier. The entire length of the jaw is 

 twenty-six inches, the molar series is ten inches and a half in extent and 

 terminates at the middle of the jaw. The condyle is transverse, but the 

 articular surface is of comparatively small size ; there appears to be a 

 second articular surface at the back part of the inner angle of the condyle ; 

 a thick, depressed, and nearly transverse process has been broken away 

 from the back of the condyle. The inner extremity of the process forms a 

 protuberance below the inner facet of the condyle. The angle of the 

 jaw is rounded off and forms, with the thick convex inferior border of the 

 horizontal ramus, a continuous curve, like that of the lower jaw in the 

 Elephant, which it likewise resembles in its short and shallow eden- 

 tulous symphysis ; but it differs from the Elephant in the extension of a 

 coarse rugged ridge along both the outer and the inner margins of the base 

 of the ascending ramus, the outer ridge ending abruptly on a line with 

 the termination of the molar series. 



The Elasmotherium resembles the Rhinoceros in the structure of the 

 condyle, especially in the division of the articular surface into an outer 

 convex horizontal facet and an inner posterior vertical and slightly con- 

 cave surface ; the correspondence is further manifested in the tubercle 

 below this surface and in the obtuse ridge running along the back of the 

 condyle which is indicated by the fractured surface. 



The Elasmotherium differs from the Rhinoceros in having the angle 

 of the jaw less produced ; and the dental canal commences nine inches 

 in advance of the condyle. The molar teeth of the Elasmotherium are 

 five in number in each ramus of the jaw, the anterior one being 

 very small ; the penultimate one the largest, measuring three inches 

 in the antero-posterior diameter, and two inches in the transverse dia- 

 meter of the crown. The enamel is remarkable for its beautiful undu- 



* eXaufia a plate, Brjpiov beast : in allusion to the plicated plates of enamel in the substance of the 

 molar teeth. 



2 F 



