150 
MAMMALIA. 
There are two in the European seas, viz.,— the Great Rorqual {Bal. hoops, Lin.),— superior in length to the com- 
mon Whale, and shunned on account of its extreme ferocity, and the small quantity of its oil ; and the Small Ror- 
qual (Bal. musculm, Lin.), which differs from the other [in its very inferior size, in its proportions, and number 
of vertebrae. There is a third in the southern seas, and also a distinct fossil species. 
On proceeding to determine the fixed analogies of the teeth throughout the different groups of Mammalia, we - 
have arrived (since most of the foregoing pages were stereotyped) at the conclusion, that no placental mammalian , 
has more than three pairs of incisors, or three pairs of true or persistent molars, (normally,) in either jaw; all 
seeming exceptions being reducible to this general proposition : whereas the Marsupials have normally four of 
each, and some even five. By persistent molars, are intended those which are not preceded by milk-teeth. 
Following, then, the indications afforded by the structure of the molars, (which we conceive to furnish the most 
available guide to sound classification,) we are next led to recognize two principal varieties of dentition among the 
Placentalia, to one or the other of which every observed modification may be definitively referred. These two 
varieties are characteristic of a great zoophagous type and a great phytophagous type. 
Where exceptions occur in the former instance, the amylaceous parts of vegetables, as fruits, seeds, and fari- 
naceous bulbs or roots, are almost exclusively resorted to; and animal products are preferred to the composition 
of the recent carcass in those few exceptive cases which, in a trivial degree, affect the latter generalization. 
The zoophagous type of dentition is obviously of a higher grade than the other, and the animals in which it 
occurs require more nutritious aliment. 
Throughout the zoophagous division, the molars are compact in texture, and the enamel never dips into their 
substance ; the basal growth of the teeth (except the pseudo-incisive canines only, in the very singular genus_ 
Cheiromys,) ceases upon the latter attaining their required size; in consequence of which they gradually wearj| 
down by attrition, till in aged animals they are not unfrequently reduced to stumps. M 
In the phytophagous division, the molars are much less compact, and the enamel generally dips into 11 
their substance in various ways; the teeth are commonly furnished with persistent formative pulps, which ]|j: 
deposit fresh substance at their base as their crowns wear away, so that they continue permanently growing. The 
exceptions that occur to this general definition do not intrinsically affect the distinctness of the present group 
from the other, and are easily understood, so that a transverse section of a molar (known to be that of a placental HI 
animal) will suffice in every instance for the determination to which it belongs. 
These two great divisions somewhat analogously subdivide each into two sections, which differ considerably in 
the general details of their organization, and most commonly in the structure of the teeth. They may be regarded 
as normal and abnormal sections. 
In the normal sections of the zoophagous and phytophagous grand divisions of Placentalia, the four sorts of fl 
teeth— incisors, canines, renewed and persistent molars— are generally present, or at least three sorts of them, 
each characterized by a particular form and structure different from the rest. In the abnormal sections, the teeth 
are commonly much more numerous, and alike in structure, and consist principally or even wholly of false 
molars ; all of them are without exception single-rooted. 
We might consider these four sections as Orders, and denominate them as follow. 
A. Zoophagous type. jr 
1. Typodontia. Normal : comprehending the Bmawa, and of Cuvier. 
2. Isodontia. Abnormal : consisting of the Cetacea of Cuvier, divested of the herbivorous subdivision. 
B. Phytophagous type. . J 
3. Diplodontia. Normal: comprising the Pachydermata, Cetacea herUvora, Rodentia, and Rtminantia of J if 
the same naturalist. ^ fl 
4 . Aplodontia. Abnormal : corresponding to the Edentata of Cuvier, divested of the Monotremata. 
These together constitute the normal or placental subclass of Mammalia; and the abnormal or ovo- viviparous 0 
subclass might range in two orders only, viz. : 
5. Heterodontia. Normal : or the Marsupiata : and ii 
6. Pseudodontia. Abnormal : or the Monotremata. II 
The Typodontia primarily subdivide into the Primates and Fera of Linnaeus, or Secundates, as the latter has« 
recently been termed by De Blainville. 
The Primates are characterized by the external distinctions popularly known, and also, it may be added, by their 
hair being of one sort only, having never any softer felt beneath it.* They separate into Cheiropodaexrd Cheiroptera. 
The Cheiropoda comprise the Bimana and Quadrumana of Cuvier, but not the marsupial handed animals, in- 
cluded under this name by Mr. Ogilby. They have never more than four incisors in either jaw, invariably pos- 
sess a coecum, have no os penis, and are born with the eyes open. They subdivide into Anthropida and Lemuria. 
The Anthropida are characterized by the general form of the head, the complete separation of the orbits from 
the temporal fossa by a bony partition, by having the incisors broad and contiguous, and vertical, or nearly so, 
in both jaws, by their anthropoid molars, &c. Their teeth form an even series, the continuity of which is only 
broken by the interspace required for the reception of the opposite canine ; and in Man only, where the canines 
are not lengthened beyond the other teeth, even this vacuity does not occur. They fall into the Catarrhini and 
Platyrrhini of Geoffroy, according to the number of false molars; and the circumstance of their being respectively 
peculiar to the Old and New Worlds, affords a presumptive argument that the human genus, which pertains 
strictly to the former, is not indigenous to America. 
* We were deceived by certain appearances in stating that exceptions to this rule existed, at pp. o7, 60. 
