530 Dr. C. I. Forsyth Major on the 
the tritubercular form of molar is to be regarded as primitive, 
or rather as the result of a process of retrogression. 
I. The Molars. 
The homologies of the cusps of the molars in the Insectivora 
have already been carefully studied by Mivart nearly thirty 
years ago*, It was shown by this author that the upper 
molars of Potamogale to a certain extent represent a tran- 
sitional stage between the more complicated molars, e. g. of 
the mole, with two triangular prisms each, and the simpler 
ones, such as those of Centetes and Hriculus, with but a single 
prism :— For each of these teeth [in Potamogale] have three 
or four very small cusps developed from the external cingu- 
lum, a very large cusp arising from the internal cingulum, 
and two median cusps, from each of which two slightly- 
marked diverging ridges proceed outwards to the external 
cingulum, forming two very narrow triangular prisms, so 
close together that a little more approximation would reduce 
them to a single prism, such as exists in Centetes and Soleno- 
don.” He also says:—‘ Potamogale shows ..... a very 
interesting approximation of the triangular prisms, the two 
external principal cusps still, however, remaining distinct, 
though in close juxtaposition. In Centetes it appears as if 
the concentration had been carried further, the two prisms 
uniting into one, as also the two external principal cusps. 
The single representative of these, however, has two small 
prominences on its inner side. In Chrysochloris we have 
the maximum of concentration, there being but a single 
triangular prism, the internal angle of which represents the 
two external principal cusps of Hrinaceus and others, while 
internal to this there is but a single prominence to represent 
the two internal principal cusps.” 
I therefore have to state that Mivart long before myself, 
at least so far as the Insectivora are concerned, represented 
the complicated character of the molars as the primitive 
condition, and maintained that the simple form had arisen 
through concentration or fusion. 
In opposition to this it was asserted by Huxley + that the 
form of molar seen in Centetes is the primitive one, and, as 
is well known, this view was subsequently supported also by 
Cope, Osborn, and Schlosser. Huxley terms the form in 
question ‘least-modified,” and, according to him, the form 
of molar exhibited by all Carnivora is easily to be derived 
* Journ. Anat. and Physiol. ii. 1868, p. 117 et seq. 
f+ Proc. Zool. Soc. London, 1880, pp. 283-284. 
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