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Show 1885.] DR. ST. G. MIVART ON THE ARCTOIDEA. 343 point where it doubles, through the cartilage covering the foramen lacerum anterius. " The modifications of the bulla mostly depend on the size of the species, it being much more swollen in the smaller ones ; the mastoid and paroccipital processes are also developed in relation to the dimensions of the species, or even the age of the individual ; in the smallest species they have hardly any projection, while in the larger ones they show the same essential structure as in the Bears. "Among the characters which I have pointed out in the base of the cranium, it will be seen that the only tangible distinction between the Bears and the Weasels is the presence of the alisphenoid canal in the former, and its constant absence in the latter. Much as I have insisted upon the importance of this character as assisting to distinguish groups, I do not consider it sufficient alone to entitle the groups which it separates to the rank of families ; neither am I prepared to admit the difference of the teeth sufficient for that purpose, these being mere adaptive modifications. In the true Bears the number of true molars is on each side two above and three below. In the Weasels it is only one above and two below. In the Subursine group, to which I must add Bassaris, it is two above and two below; and among these it is only Ailurus which possesses the alisphenoid canal." He further expressed his views in a synopsis as follows :- " Fam. URSIDJE. "Auditory bulla rising suddenly on its inner side, and more or less flattened off towards the meatus. "Paroccipital process prominent, and neither flattened on the surface of the auditory bulla, nor laterally compressed. "Foramen condyloideum exposed. A considerable foramen gle-noideum. "No caecum. No Cowper's glands. " Prostate gland not salient, being contained in the thickened walls of the urethra. " Subfamily URSINA (of general geographical distribution). "A. distinct alisphenoid canal. " Internal carotid artery reappearing externally, after passing through its canal, and doubling back to enter the cranium. 2 " True molars on each side §. "Crsus (including the subgenera). " Subfamily AILURINA (confined to India). "A distinct alisphenoid canal. 2 " True molars on each side r2. "Ailurus. 23* |