MARSUPIALIA. 



297 



veloped, and the conjunctiva covering its free 

 margin is stained black. 



In the Kangaroo I found the dark pigment 

 on both the inside and outside of the choroid, 

 and the ciliary processes very well developed. 

 The lens is proportionally large. In the dead 

 Kangaroo the radiated muscle of the iris is 

 much contracted, and the pupil widely open. 

 Beneath the upper eyelid in the Kangaroo 

 there is a cartilaginous ridge having the con- 

 junctiva reflected over it. 



Organ of taste. The tongue is well deve- 

 loped and freely moveable in all the ,\larsu- 

 pialia, and the epithelium covering the simple 

 papillae of its dorsum is never condensed into 

 spines. In the carnivorous species, as the 

 Dasyuri, the conical papillae are minute and 

 soft, but directed backwards so as to give a 

 slight roughness to the tongue when stroked in 

 the opposite direction. Under a lens they 

 appear like fine shagreen. Near the base of 

 the tongue in Dasyurus viverrinus there are 

 three fossulate papilla, in triangle, with the 

 apex towards the epiglottis. There is a small 

 li/tta beneath the tip of the tongue. 



In the Perameles, besides the minute and 

 generally diffused simple papillae, there are 

 others of larger size, placed at distances of 

 nearly a line apavt, and raised about a third of 

 a line above the surface of the dorsum. The 

 fossulate or glandular papillae correspond in 

 number and arrangement with those of the 

 Dasyures, but the entire tongue is relatively 

 longer and more slender, especially in Per. 



lagllttS. 



In some species of Opossum, as Didelphys 

 Philander, the margin of the tongue is fringed 

 with a series of fine long papillae. 



In the Phalangers there is a thickening at 

 the edge of the fraenum linguae, but no true 

 lytta. The dorsal papillae resemble those of 

 the Dasyures, but are somewhat more obtuse. 



In the Kangaroo there is a callous ridge 

 along the middle of the under surface of the 

 free extremity of the tongue, and a corresponding 

 furrow along the dorsum ; the latter is common 

 to all the Marsupials. In the Wombat and 

 Koala the dorsum of the tongue rises some- 

 what abruptly from a furrow surrounding its 

 base ; its form is narrow, moderately deep, 

 diminishing in this respect to the tip, which is 

 rounded. In both the Kangaroo and Koala 

 there is a single large fossulate papilla near 

 the base of the tongue. 



The palate is sculptured in most Marsupials 

 with transverse ridges. These are most nume- 

 rous in the Bandicoots, being fourteen in the 

 Perameles nasula, and are slightly curved for- 

 wards. The roughness thus produced must aid 

 the tongue in retaining small insects. 



DIGESTIVE SYSTEM. 



Month. The various modes of locomotion, 

 resulting from the different modifications of the 

 osseous and muscular systems observable in the 

 several families of Marsupialia, relate to the 

 acquisition of as various kinds of alimentary 

 substances, which necessarily require for their 

 assimilation as many adaptations of the diges- 

 tive organs. 



Food, means of obtaining it, instruments 

 for preparing and mechanically dividing it, 

 cavities, canals and glands for chemically 

 reducing and animalizing it, form a closely 

 connected chain of relationships and interde- 

 pendencies. The usual sequence of anatomical 

 description has here been followed in com- 

 mencing with the consideration of the passive 

 and active organs whose office it is to carry the 

 stomach to the food and the food to the mouth, 

 and we have now to describe the preparatory 

 mechanical instruments in digestion, and the 

 modifications and appendages of the alimentary 

 canal. 



The jaws of the Marsupialiaare covered by well- 

 developed fleshy lips ; the upper lip is partially 

 cleft in the Kangaroos, as in some of the Ro- 

 dents ; the muzzle is clad with hair in the 

 Great Kangaroo and a few other species of 

 Macropus, but in other Marsupialia it is naked 

 and generally red from the vascularity of the 

 integument. 



The masticatory muscles of the jaws consist 

 in the Marsupial, as in other Mammalia, of the 

 temporal, the masseter, the external and in- 

 ternal pterygoids, and the digastricus. They 

 are chiefly remarkable for the large proportional 

 size of the masseter and internal pterygoid; the 

 great developement of the latter muscle is con- 

 stant in all the Marsupials, and is the condi- 

 tion of the peculiarly large and inflected angle 

 of the lower jaw. The relative size of the 

 masseter, as compared with the temporal mus- 

 cle is greater in the herbivorous than in the 

 carnivorous species, but this difference is 

 much less in the Marsupial than in the cor- 

 responding placental genera. The extent of 

 origin of the temporal ?nuscle is indicated by 

 the various conditions of the temporal and pa- 

 rietal crests ; the inner surface of the zygomatic 

 arch always affords origin to a portion of the 

 fibres of this muscle, and in some species, as 

 in the Koala, to all that poition of it which is 

 inserted into the external fossa of the coronoid 

 process and ascending ram us of the jaw, the 

 fibres from the temporal and parietal bones 

 being implanted on the inner side of the coro- 

 noid process. The masseter takes its origin by 

 a strong band of tendinous and carneous fibres 

 from the inferior and anterior part of the zy- 

 goma ; the muscle expands as it is directed 

 backwards, and is inserted into the ridge which 

 bounds the external temporal fossa of the as- 

 cending ramus, and into the outer side of the 

 inflected angle of the outer jaw. The external 

 pterygoid takes its origin from the temporal 

 plate of the sphenoid and the base of the 

 pterygoid plate anterior to the sphenoidal 

 bulla ; the fibres converge to be implanted 

 into the inner projecting side of the condyle 

 of the jaw. The internal pterygoid arises 

 from the outer depression of the longitudi- 

 nally extended pterygoid plate already men- 

 tioned as characterizing the cranial structure 

 of the Marsupials, and is implanted along the 

 inner surface of the inflected angle of the jaw. 

 The digastricus arises from the ex-occipital 

 process ; its fibres expand, and are inserted 

 into the lower margin of the maxillary ramus, 

 anterior to the commencement of the inflected 



