described by Professor Cope 1 in the postparietal and mastoid which 

 occur in Ursus, but are said to be absent in Canis, are present in 

 Amphicyon. So far, however, as we can see, the presence or absence 

 of those foramina cannot be regarded as diagnostic of Ursus and 

 Canis, although they are generally more strongly developed in 

 the former. Amphicyon may, indeed, be considered as a very 

 generalised Dog, with affinities to the Bears in the structure of 



its limbs. Dinocyon is a still larger form, 

 from the Middle Miocene of France, 

 which, so far as its teeth are concerned, 

 connects Amphicyon with the Ursoid 

 genus Hycenarctus so closely as to render 

 it absolutely impossible to indicate any 

 characters of family importance by which 

 they can be distinguished. The upper 

 carnassial of Dinocyon is unknown. For 

 other genera, see p. 562. 



Section ARCTOIDEA. 



This section includes a considerable 

 number of forms which agree in the 

 essential characteristics of the struc- 

 tures of the base of the cranium and 

 reproductive organs, and in the absence 

 of a caecum to the intestinal canal. 

 They have no Cowper's glands, but 

 there is a rudimentary prostate and a 

 large cylindrical penial bone ; while all 

 the members of the group have five 

 completely developed toes on each foot. 

 Considerable diversity is found in the 

 characters of the base of the skull in 

 the various forms, but the following 

 features are common to all. The cavity 

 . .. , , , of the auditory bulla is simple, and has 



Fio. 254. Right half of the palatal J ... .... , 



aspect of the cranium of the Raccoon no trace of a dividing septum ; the 

 (Procyon lotor). Letters as in Fig. s, inferior lip of the auditory meatus 



fwTp. io7 m the PrOC ' ZO L SOC ' ( am > Fi S' 254 > is considerably pro- 

 longed ; the paroccipital process ( p) of 



the exoccipital is more or less triangular, directed backwards, 

 outwards, and downwards, and standing quite apart from the 

 bulla ; the mastoid process (m) of the periotic is always widely 

 separated from the paroccipital, and generally very prominent; 

 the carotid foramen (car) is large, and placed on the inner margin 



1 Proc. Amcr. Phil. Soc. vol. xviii. p. 452 (1880). 



