311—134 INDIAN TERTIARY AND POST-TERTIARY YERTEBRATA. 
As special characters of particular forms, which are not found in other highly 
specialized species, may he mentioned the suppression of pm. 1 , and of the tubercle 
of pm. 4 . The great development of the talons of the premolars which occurs in the 
most generalized forms is not continued above II. striata ; and it is noteworthy that 
in II. grceca , which retains the generalized character of a large m, 1 and the presence 
of pm. 1 and m. 2, m. 1 has lost its inner cusp. 
It will be observed from the description of the dentition of those groups that 
an almost precisely analogous series of developments occurs among the dogs and the 
cats, and to a minor extent among the bears ; and it will, therefore, be apparent, as 
has been already mentioned, that these developments must have occurred inde- 
pendently of one another ; as if the different groups had been, so to speak, running 
a race along similar parallel roads to similar common goals, which all had attained. 
Although the dentition of the more generalized hyaenas is, with the exception of the 
absence of m.-2 , very similar to that of Ictitherium (which is probably near the 
original ancestry of the group) ; while in the suppression of certain teeth and the 
form of the carnassials the higher forms are more like the higher Felidce , the fact that 
the precarnassial cheek-teeth of the latter are always of the elongated form 
characteristic of the most generalized hyaenas, proves that the higher hyaenas are 
genetically entirely distinct from the Fclidce. The relationship between the lowest 
hyaenas and Ictitherium is sb extremely intimate that it may be well doubted whether 
it is possible to draw any valid distinction between the Hycenidce and the Viverridce ; 
while the genus Lcpthycena brings the Hycenidce into close connection with the Felidce. 
With regard to the mutual genetic relations of the hyaenas, it has already been 
mentioned that II. sivalensis may have belonged to the direct parental stock of U. 
brunnea ] which it connects with the generalized II. macrostoma : beyond this, however, 
it cannot be said that there is a probability of any one species in the foregoing list 
being the direct ancestor of another. The minute gradations occurring between 
many of these forms leave, however, little room for doubt that they have taken 
origin from a common stock, somewhat after the order in which they are arranged 
above ; and afford as good an instance of progressive modification as can be found 
among any group of the Mammalia. 
It is worthy of note in connection with the canoid characters of the skull of 
II. macrostoma that the hinder premolars of the mandible have a marked resemblance 
to those of the S. African Lycaon , in which there is a distinct- anterior talon to pm. 4, 
generally wanting in the dogs, though present in the so-called hysenoid wolf of 
Spritsail cave, 1 and in a less degree in some of the domestic races. 
“ Pal. Mem.,” vol. II., pi. 36. 
