CANID^E 555 



of the four molar teeth as a survival of a condition of the dentition 

 exhibited by the common ancestors of the existing Canidce and the 

 existing carnivorous Marsupials. There is, however, at present no 

 palaeontological proof of this, as none of the numerous fossil forms 

 of Canidce yet discovered have more than the normal number of molars. 

 Extinct Genera. A large number of fossil Carnivora have been 

 described from various Tertiary deposits which are more or less 

 closely allied to the existing Canidce, although, as already men- 

 tioned, connecting the latter so closely on the one hand with the 

 Fiverridce and on the other hand with the Ursidce, that it is almost, 

 if not quite impossible to say where one family begins and the other 

 ends. A few only of the more important of these annectant types 

 will be mentioned here. Temnocyon, of the Miocene of the United 

 States, is a true Dog, which agrees with Idicyon in having a secant 

 hind talon to the lower carnassial, but preserves a generalised char- 

 acter in having an entepicondylar foramen to the humerus. An 

 extremely interesting form is Cynodidis, of the Middle Tertiaries 

 of Europe and the United States, which (as now restricted by 

 Dr. Schlosser) includes a number of species mostly not larger than 

 Foxes. The dental formula is generally the same as in Canis, but 

 (as in that genus) the last lower molar may be absent. The teeth 

 are very like those of the Viverridce, the lower carnassial never being 

 greatly elongated antero-posteriorly, and its inner cusp being situ- 

 ated immediately on the inner side of the hinder lobe of the blade, 

 instead of somewhat behind it, as is the case in most Dogs. ' In 

 the skull the auditory bulla is inflated, but is said to have no 

 distinct septum ; while the humerus invariably has an entepicondylar 

 foramen. It is suggested that Cynodidis is not far removed from 

 the ancestral type of many of the Viverroids and Ganoids, and may 

 itself have been derived from the undermentioned genus Amphicyon. 

 M. Boule considers, indeed, that from the resemblance of the Plio- 

 cene Canis megamastoides (p. 553) to Cynodidis we ought to regard 

 the Foxes and Jackals as the descendants of Cynodidis, while the 

 Wolves have been derived directly from Amphicyon. The last 

 named genus, which includes some species as large as a Bear, is 

 found in the Upper Eocene and Lower Miocene of Europe, and is 

 represented in the Miocene of the United States by the allied 

 Daphcenus. It is characterised by the presence of three upper 

 molars thus bringing up the dental formula to the full Eutherian 

 mimber; by the five digits on all the feet, which were plantigrade; 

 and by the presence of a third trochanter to the femur and an 

 entepicondylar foramen to the humerus. The teeth are essentially 

 those of a dog, and the base of the skull is also dog-like, although 

 it is highly probable that the auditory bulla had no trace of a 

 septum. According, however, to Dr. Filhol l the minute foramina 

 1 Arch. Mus. Lyan. vol. iii. art. 1, p. 85 (1881). 



