OCR Text |
Show 1885.] DR. ST. G. MIVART ON THE ARCTOIDEA. 345 the bulla can be seen, or if a probe is passed into the meatus, obstacle will prevent its touching the inner wall. Whatever the diversity of development of the bulla, it always has its greatest prominence near the middle of the inner border, and slopes away from that point, not only externally, but also forwards and backwards. " (2) The inferior lip of the external auditory meatus is always considerably prolonged. "(3) The paroccipital process is more or less triangular, and directed backwards, outwards, and downwards, standing quite aloof from the bulla. This relation depends chiefly on the want of development of the posterior portion of the bulla, and is absent or obscure in Mustela alone. "(4) The mastoid process is widely separated from the paroccipital, and generally very prominent. "(5) The carotid foramen is always large, and placed usually near the middle, but sometimes more posteriorly, on the inner margin of the bulla. It is generally very conspicuous, but sometimes partially concealed by the projecting lip of the basioccipital. "(6) The condyloid foramen is distinct and exposed, and although sometimes partially overlapped posteriorly by a ridge of bone passing from the paroccipital to the condyle, it is never sunk into a common opening with the foramen lacerum posticum. " (7) The glenoid foramen is always present, and generally very conspicuous. In Enhydris it is least so. "(8) The alisphenoid canal is present in the true Bears and Ailurus, absent in all the others. Hence it cannot he used to characterize the entire group, though useful in aiding its subdivision. " The group thus defined is, I think, too extensive, and presents too great variation among its members, in dentition and external characters, to constitute a family, as proposed by Mr. Turner. I would rather regard it as a primary section of the fissipedal Carnivora, to which the name of A R C T O I D E A might be given. "I perfectly agree with Mr. Turner that it is further divisible into four chief sections, or families as I should call them-the Ursida, Ailurida, Procyonida, and the Mustelida. " Of the Arctoidea, the true Bears are the most specialized or aberrant; they form a very compact group, distinguished by their very characteristic dentition, and their completely plantigrade mode of progression. They have a very wide geographical range. On the other hand the Procyonida, though few in numbers aud restricted to the warmer and temperate parts of the American continent, are structurally less closely connected, at least if the singular Cercoleptes is truly a member of this group. Except for the increased number of the molar teeth, which is the only definite character by which they can be separated from the Mustelida, I see no reason for considering the Procyonida more nearly allied to the Ursula than are the other families of the group, or for speaking of them as specially ' subursine.' "Ailurus (an unfortunate name for an animal so essentially Arctoid) appears to m e to be an isolated form. Its dentition, though re- |