Marsupials may be defined as viviparous (that is non-egglaying) mammals, in which the young are born in an imperfect condition, and almost immediately attached to the teats of the mammary glands; the latter being generally enclosed in a pouch, and the front edge of the pelvis being always furnished with epipubic or "marsupial" bones.
It may open either forward or backwards; and although present in the great majority of the species, and enclosing the teats, it may, as in many of the opossums, be completely absent, when the teats extend in two rows along the whole length of the under-surface of the body.
Whether a pouch is present or not, the young are born in an exceedingly imperfect state of development, after a very short period of gestation, and are immediately transferred by the female parent to the teats, where they remain firmly attached for a considerable time; the milk being injected into their mouths at intervals by means of a special muscle which compresses the glands.
The latter may, however, be split up into several sub-generic groups, such as Metachirus, Philander, Marmosa (Micoureus or Grymaeomys), Peramys, Dromiciops, &c. The small South American forms included in Marmosa, which lack the pouch, and have numerous teats, and molar teeth of a primitive type, are doubtless the most generalized representatives of the group (see Opossum; and WATER-Opossum).
The pouch is incomplete, with two lateral folds, and the number of teats six.
Their abdominal bones are like those of the marsupials; and they are furnished with pouches for their young, but have no teats, the milk being distilled into their pouches from the mammary glands.
Teats two, inguinal in position.
The stomach is simple, the caecum large and capacious, the placenta diffused, and the teats inguinal.
Teats two, inguinal.
Then again, the ears are large in proportion to the head, the pupil of the eye is elliptical and vertical when in a strong light, and the female has six pairs of teats, in place of the three to five pairs found in dogs, wolves and jackals.
The teats are usually few, and inguinal, but may be numerous and abdominal (as in Suina), although they are never solely pectoral.
Teats either few and inguinal, or numerous and abdominal.
Teats 2 or 4.
These rodents are characterized by the imperfectly rooted cheek-teeth, imperfect clavicles or collar-bones, cleft upper lip, rudimentary first front-toes, smooth soles, six teats and many cranial characters.
The teats vary in number from a single abdominal pair in the guinea-pig to six thoracico-abdominal pairs in the rats; while in the Octodontidae and Capromyidae they are placed high up on the sides of the body.
In Xerus itself, which is represented by the terrestrial African spiny squirrels, the ears are short, there are only two teats, and flat spines are mingled with the fur; while the skull, and more especially the frontals, is elongated, with a very short post-orbital process, and the crowns of the molars are taller than usual (see Spiny Squirrel).
The teats are either four or six.
Australia is the home of the group of jumping species, known as jerboa-rats, characterized by the elongation of the hind limbs, arranged under the genera Notomys, Dipodillus, Ammomys and Conilurus, distinguished from one another by the structure of the molars and the number of teats and foot-pads, the second being further characterized by its long ears.
The upper lip is cleft, the jugal lacks an inferior angle, the fore part of the skull is short and broad; the cheek-teeth are partially rooted, with external and internal enamel-folds, the soles of the feet are smooth, there are six pairs of teats, the clavicles are imperfect and the tail is not prehensile.
Female has six teats, of which four are inguinal and two axillary, and the placenta is zonary and deciduous.
~ belly and teats, value b; from I hi, belly.
Both in this species and the slow loris there is a pair of rudimentary abdominal teats in addition to the normal pectoral pair.
Cretan coins represent the infant Zeus being suckled by the goat; other Greek coins exhibit him suspended from its teats or carried in the arms of a nymph (Ovid, Fasti, v.