Volltext: The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri (4)

both jaws ; the second premolar displaces 
the first normally developed deciduous molar; 
the third upper premolar displaces and suc¬ 
ceeds the deciduous sectorial, which has a 
sharper and more compressed blade, and a 
relatively smaller internal tubercle, than the 
permanent sectorial. This tooth displaces 
the last deciduous molar, which is a tubercular 
tooth, resembling in form the first of the two 
upper permanent tuberculars ; these coming 
into place without pushing out any prede¬ 
cessors, enter into the category of true molar 
teeth. In the lower jaw the third premolar 
displaces the deciduous sectorial, which has 
three trenchant lobes and a relatively smaller 
posterior talon than the permanent sectorial. 
The fourth premolar displaces the third 
or tubercular milk-molar. The permanent 
sectorial and tubercular molars displace 
no predecessors, and are therefore m. 1 and 
m. 2. 
The first premolar, p. 1, is not developed 
at any period in the Mangues (Crossarchus), 
the Suricates (Ryzœna), or the Mangusta 
•paludinosa ; these Viverrines, therefore, retain 
throughout life more of the immature cha¬ 
racters of the family, and in the same degree 
approach in the numerical characters of their 
dentition to the more typical Carnivora. 
The alternate interlocking of the crowns of 
the teeth of the upper and lower jaws, which is 
their general relative position in the Carnivora, 
is well marked in regard to the premolars 
of the Viverridce (fig. 580, IV.) : as the lower 
canine is in front of the upper, so the first 
lower premolar rises into the space between 
the upper canine and first upper premolar ; 
the fourth lower premolar in like manner fills 
the space between the third upper premolar 
(p. 3) and the sectorial tooth (p. 4), playing 
upon the anterior lobe of the blade of that 
tooth which indicates by its position, as by 
its mode of succession, that it is the fourth 
premolar of the upper jaw. The first true 
molar below, modified as usual in the Car¬ 
nivora to form the lower sectorial, sends the 
three tubercles of its anterior part to fill the 
space between the sectorial (p. 4) and the 
first true molar (m. 1) above. In the Mu- 
sangs the lower sectorial is in more direct 
opposition to its true homotype, the first 
tubercular molar in the upper jaw ; and these 
Indian Viverridce (Paradoxuri) are the least 
carnivorous of their family, their chief food 
consisting of the fruit of palm -trees, whence 
they have been called “ Palm-cats.” 
Hyæna.— The dentition of this genus pre¬ 
sents a nearer approach to the strictly car¬ 
nivorous type by the reduction of the tuber¬ 
cular molars to a single minute tooth on each 
side of the upper jaw, the inferior molars 
being all conical or sectorial teeth : the molar 
teeth in both jaws are larger and stronger, 
and the canines smaller in proportion than in 
the Feline species, from the formula of which 
the dentition of the hyæna differs numerically 
only in the retention of an additional pre¬ 
molar tooth, p. 1 above and p. 2 below, 
on each side of both jaws. The dental 
formula of the genus Hyæna is: — in. ——-, 
1—1 4—4 1—1 3—3 
c‘ JUT5 Pm' 3H3’ m‘ 1ZI7: =: 34. The 
crojvns of the incisors form almost a straight 
tranverse line in both jaws, the exterior 
ones, above, being much larger than the 
four middle ones, and extending their long 
and thick inserted base further back : the 
crown of the upper and outer incisor (i. 3.) 
is strong, conical, recurved, like that of a 
small canine, with an anterior and posterior 
edge, and a slight ridge along the inner side 
of the base. The four intermediate small 
incisors have their crown divided by a trans¬ 
verse cleft into a strong anterior, conical lobe, 
and a posterior ridge, which is notched ver¬ 
tically; giving the crown the figure of a 
trefoil. The lower incisors gradually increase 
in size from the first to the third ; this and 
the second have the crown indented ex¬ 
ternally ; but they have not the posterior 
notched ridge like the small upper incisors ; 
the apex of their conical crown fits into the 
interspace of the three lobes of the incisor 
above. The canines have a smooth convex 
exterior surface, divided by an anterior and 
posterior edge from a less convex inner side : 
this surface is almost flat and of less relative 
extent in the inferior canines. The first 
premolar above (p. 1) is very small, with a 
low, thick, conical crown : the second presents 
a sudden increase of size, and an addition of 
a posterior and internal basal ridge to the 
strong cone. The third premolar exhibits 
the same form on a still larger scale, and is 
remarkable for its great strength. The pos¬ 
terior part of the cone of each of these 
premolars is traversed by a longitudinal ridge. 
The fourth premolar is the carnassial tooth, 
and has its long blade divided by two notches 
into three lobes, the first a small thick cone, 
the second a long and compressed cone, the 
third a horizontal sinuous trenchant plate : a 
strong triedral tubercle is developed from the 
inner side of the base of the anterior part of 
the crown. The single true molar of the 
upper jaw (m. l) is a tubercular tooth of 
small size : transversely oblong in the Hyæna 
vulgaris and H.fusca; smaller and sub-cir¬ 
cular in the Hyæna crocuta ; still smaller and 
implanted by a single fang in the Hyæna 
spelæa : in all the existing species of Hyæna it 
has two fangs. The first premolar of the lower 
jaw (p. 2) fits into the interspace between the 
first and second premolars above, and answers, 
therefore, to the second lower premolar in 
the Viverridæ : it is accordingly much larger 
than the first (p. 1) above ; it has a ridge in 
the fore-part of its cone, and a broad basal 
talon behind. The second (p. 3) is the 
largest of the lower premolars, has an anterior 
and a posterior basal ridge, with a vertical 
ridge ascending upon the fore as well as the 
back part of the strong rounded cone : the 
third premolar (p. 4.) is proportionably less 
in the Hyæna crocuta than in the H. vulgaris: 
its posterior ridge is developed into a sma-i 
cone; the last tooth (m. 1) is the sectorial,


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