192 
MASARU NAGAO 
The results of my study apparently oppose these three conclusions 
by Spee. I present below the argument for my own views. 
As to point one: Spee states that in rodentia and camivora the 
curve of Spee is absent. In these forms the tuberculum articulare 
is also absent, while in the horse, Cervus elephas, Cervus dama, small 
monkeys and man, which show the curve of Spee, the tuberculum 
articulare is present. I have examined two species of rodentia, the 
guinea-pig (Cavia cutleri) and the muskrat (Fiber zibethicus). In 
the case of the guinea-pig the tuberculum articulare is absent and the 
animal does not possess the curve of Spee. In fact a line drawn con- 
necting all summits of the buccal cusps of the bicuspids and molars 
is nearly a straight line. On the other hand, in the case of the musk- 
rat, not only is the curve of Spee evident, but the degree of the curva- 
ture is considerable, as can be inferred from the small length of the 
radius of the circle (table 9), yet this animal does not possess the 
tuberculum articulare, as it should according to Spee. 
In the case of carnivora, my observations agree with those of Spee 
that the skulls possess neither the curve of Spee nor the tuberculum 
articulare. It is well known that the temporo-mandibular joint in 
camivora is quite different from that in most of the other mammals. 
For example, in FeHdae the fossa is complete and therefore fits the 
form of the condyle (an interarticular cartUage being, however, inter- 
posed) with such accuracy that only a single motion is possible; 
consequently, in the process of opening the mouth, any part of the 
mandible must describe an arc of a single circle, of which the condyle 
is its center. The term "ginglymus" is used to describe such a joint, 
as was explained earlier. 
All the carnivora examined by me possess the ginglymus joint, 
and the curved line touching the summits of the buccal cusps of the 
bicuspids and molars represents an undulating curve, as was described 
in section II in connection with the skull of the raccoon. Again, 
according to Spee, the tuberculum articulare is absent in all carniv- 
ora. However, in the cases of Didelphys marsupialis (opossum) 
representing the marsupials, and of Dycotyles sp. (peccary) repre- 
senting the artiodactyla, I found that, although these animals possess 
a temporo-mandibular joint resembling that of carnivora, and con- 
sequently the tuberculum articulare is absent, nevertheless the curved 
