Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/430

Rh 408 MAMMALIA [CHIKOPTEKA. notice that in the only family of insectivorous Bats wanting the tragus, the Rhinolophidx, the auditory bullae ossese reach their greatest size, and the highly sensitive nasal appendages their highest development ; also in the group Molossi the ear-conch is di vided by a prominent keel ; and the antitragus is remark ably large in those species in which the tragus is minute (see fig. 66, a). In the frugi- vorous Bats, as might be expected, the form of the ear-conch is very simple, and but slightly variable through out the species. In all Bats the ears are extremely mobile, each mov- c inw independently at theFio. 66. Head of HMOSSUS gjaucmus. .?, . ., L. J, ml. Pobson, Proc. Zool. Soc., 1S76. a, Will 01 the animal. J hlS antitragus; ft, keel of the ear-conch; has been observed by the c, notch behind antitragus. writer even in the frugivorous Pteropodidx, in which the peculiar vibratory movements noticed by Mr Osburn in Artibeus perspicillatus may also be seen when the animals are alarmed. The opening of the mouth is anterior in most species, but in many it is inferior, the extremity of the nose being more or less produced beyond the lower lip, so much so indeed in the small South-American species Rynchonycteris naso as to resemble that of the Shrews. The lips exhibit the greatest variety in form, which will be specially referred to under each family. The absence of a fringe of hairs is very characteristic of all fruit-eating Bats, and probably always distinguishes them from the insectivorous species, which they may resemble in the form of their teeth and in other respects. The oesophagus is narrow in all species, and especially so in the sanguivorous Desmodontes. The stomach presents two principal types of structure, which correspond respec tively to the two great divisions of the order, the Megachiroptera and the Microchiroptera ; in the former (with the exception of Harpyia) the pyloric extremity is more or less elongated and folded upon itself, in the latter it is simple, as in Insectivora vera ; a third exceptional type is met with in the sanguivorous Desmodontes, where the left or cardiac extremity is greatly elongated, forming a 1 jng narrow caecum-like appendage. The intestine is com paratively short, varying from one and a half to four times the length of the head and body, being longest in the frugivorous, shortest in the insectivorous species. In Rhinopoma microphyllum and Megaderma spasma only has a very small caecum been found. The liver is characterized by the great size of the left literal lobe, which occasionally equals half the size of the whole organ ; the right and left lateral fissures are usually very deep ; in Megachiroptera (Harpyia excepted) the Spigelian lobe is ill-defined or absent, and the caudate is generally very large, but in Microckiroptcra, on the other hand, the Spigelian lobe is very large, while the caudate is small, in most species forming a ridge only. The gall bladder is generally well developed and attached to the right central lobe, except in Rhinolophidse, where it is connected with the left central. In most species the hyoid bones are simple, consisting of a chain of slender, elongated, cylindrical bones connect ing the small basi-hyoid with the cranium, while the pharynx n short, the larynx shallow with feebly developed vocal cords, and guarded by a short acutely-pointed epiglottis, which in some genera (Harpyia, Vampyrus, e.g.} is almost obsolete. In the Epomophori, however, we find a remarkable depart ire from the general type: the pharynx is long and very capacious, the aperture of the larynx far removed from the fauces, and, opposite to it, a canal, leading from the narial chambers, and extending along the back of the pharynx, opens ; the laryngeal cavity is spacious and its walls are ossified ; the hyoid bone is FIG. 67. Head and Keck of Epomophonu franqueti (adult male, natural size). Dobson, Proc. Zool. Soc., 1881. The anterior (a.ph.s) and posterior (p.ph.s) pharyngeal sacs are op ned from without, the dotted lines indicating the points where they communicate with the pharynx ; s, thin membranous septum in middle line between the anterior pharyngeal sacs of opposite sides; s.m, sterno- mastoid muscle separating the anterior from the posterior sac. quite unconnected, except by muscle, with the cranium ; the cerato-hyals and epi-hyals are cartilaginous and greatly expanded, entering into the formation of the walls of the pharynx, and, in the males of three species at least, sup porting the orifices of a large pair of air-sacs communicat ing with the pharynx (see fig. 67). In extent, peculiar modifications, and sensitiveness, the cutaneous system reaches its highest development in this order. As a sensory organ its chief modifications in con nexion with the external ear, and with the nasal and labial appendages, have been described when referring to the nervous system. It remains therefore to consider its relative development as part cf the organs of flight. The extent and shape of the volar membranes depend mainly on the form of the bones of the anterior extremities, and on the presence or absence of the tail. Certain modifications of these membranes, however, are met with,, which evidently do not depend on the skeleton, but are related to the habits of the animals, and to the manner in which the wing is folded in repose. The volar membranes consist of (1) the &quot; antebrachial membrane,&quot; which extends from the point of the shoulder along the humerus and more or less of the forearm to the base of the thumb, the metacarpal bone of which is partially or wholly included in it ; (2) the &quot; wing-membrane,&quot; which is spread out between the greatly elongated fingers, and extends along the sides of the body to the posterior extremities, generally reaching to the feet ; and (3) the &quot; interfemoral membrane,&quot; the most variable of all, which is supported between the extremity of the body, the legs, and the calcanea (see fig. 65). The antebrachial and wing membranes are most developed in those species which are fitted only for aerial locomotion, and which when at rest hang with the body enveloped in the wings ; but in the family Eml&amp;gt;allomiridse r especially in the subfamily Molossinse (the species of which are, 01 all Bats, the best fitted for terrestrial progression), the antebrachial membrane is reduced to the smallest size, and is not developed along the forearm, leaving also the