Cope.] -jUb [April 4, 



little doubt that the remainder of the tooth was, as in that genus, a conic 

 tubercle. The most remarkable feature of the genus is seen in the 

 inferior canines. These are very large teeth, and are directed im- 

 mediately forwards, as in the case of the cutting teeth of rodents. 

 They work with their extremities against the retrorse crowns of the two 

 external incisors above; and laterally against the superior canine. They 

 are separated by a space about equal to the diameter of one of them. 

 In this space I rind no alveoli nor roots of teeth ; the outer alveolar wall 

 extends far beyond the inner. The latter terminates opposite the middle 

 of the superior canine. It may be that there are no inferior incisors. 



Some of the vertebrae display stout triangular neural spines ; on the 

 lumbars the posterior zygapophyses are embraced laterally by the 

 grooved correspondents of the succeeding vertebra. Some of the caudal 

 vertebrae are long, slender and without neural arch, indicating that this 

 genus, like Mesonyx, had a long slender tail. 



Affinities. Having described the available parts of this form, it re- 

 mains to consider its place in the zoological system. The structure of 

 the dentition of the upper jaw, with the mode of articulation of the 

 mandible remove it from such orders as Bodentia and Edentata; the 

 only remaining ones with which it is necessary to compare it are the 

 Perissodactyla, Proboscidia and Carnivora. As many of the diagnostic 

 bones are wanting, it is necessary to rely on collateral and empirical 

 indications of relationship. From tapiroid types the development of 

 the tympanic region distinguishes it. From Proboscidians the slender 

 feet and reduced ulna, as well as the longitudinal crests of the teeth 

 separate it. It then remains to compare it with Perissodactyles of the 

 types which possess strong canine teeth. In points of resemblance to 

 these we have the flat claws and separate scaphoid and lunar bones, 

 nevertheless the greater number indicate truer affinity to the Carnivora. 

 Such are the external transverse glenoid cavity, the teeth with longi- 

 tudinal crests, the slender digits, the well developed tympanic bone ; 

 confirmatory are the large canine teeth, the incomplete orbit, and the 

 projecting inner condyle of the humerus. The form of the claws is not 

 absolutely incompatible with the same order, as it is approximated by 

 some of the Seals. 



Among Carnivora, the feet are like both dogs and bears. The very 

 prominent postglenoid ridge, and the narrow tympanic chamber* are 

 decided points of resemblance to the bears, but the cavum tympani is 

 even less expanded than in those animals. The characters of dentition 

 are more like those of the Hyainodonlidai and Mesonyx than any other 

 group, and even the remarkable incisor-like inferior canines are ap- 

 proximated by the anteriorly directed canines of Hyamodon leptorhynchus, 

 Laiz. et Par. 



As a summary, it may then be concluded that the genus Synoplotlteriuni 

 is a Carnivore, presenting a number of points of resemblance to the 

 bears, and to the extinct 'Hycenodons; but that its distinct scaphoid 



* See Prof. Flower's Osteology of Mammalia on this point. 



