598 CHEIROPTERA. 



it would require the constant exertion of such The tarsus is composed of the usual bones. 



a degree of antagonizing muscular force to There is a peculiarity in the heel, however, 



prevent it, as would be incompatible with the which is worthy of notice. There is a long, 



essential structure of these organs of flight. slender, pointed, bony process from the pos- 



The carpus is of a very peculiar structure, terior part of the foot which is inclosed within 



The first series of bones consists but of two ; the folds of the margin of the iriterfemoral 



one very large, on which the radius rests, and membrane, and extends about half-way to the 



which is probably formed of the three outer tail. Whether this process is a portion of the 



bones, the scaphoid, the semilunar, and the os calcis, according to Cuvier, or a distinct 



cuneiform bones ; the other extremely small, bone according to Daubenton, it is perhaps 



which is undoubtedly the pisiform, on the ulnar difficult to decide ; but the opinion of Meckel 



side. is probably the correct one, that it is nothing 



The second series consists of the four bones more than a development of the tuberosity of 



of which it is usually constituted. that bone, remaining disunited from its body. 



The metncarpal bones and phalanges of all The metatarsal bones are rather short, slender, 



the fingers excepting the thumb are extremely and of nearly equal length, 



elongated. They extend outwards and down- The phalanges of the five toes are nearly 



wards in a slightly curved direction to the equal, the inner toe reaching almost to the 



margin of the flying membrane, the second same length as the others, in consequence of 



finger being the shortest and extending to the the greater elongation of its first phalanx. 



upper angle of the outer margin, the third, The ultimate phalanges are furnished with 



fourth, and fifth to the inferior margin of the hooked nails, by which these animals constantly 



membrane. There is a slight enlargement at suspend themselves when at rest with the head 



the articulation of the metacarpal bones with downwards. 



the phalanges ; but otherwise these bones are The whole of this structure is so perfectly 



extremely slender and cylindrical. The thumb adapted to the peculiar habits of the animals, 



is of no extraordinary length, and the ultimate as to require no comment. The great deve- 



phalanx is hooked and sustains a nail, by lopment of the ribs, sternum, and scapula, for 



which the animal is enabled to climb on any the attachment of strong muscles of flight, the 



rough perpendicular surface, or to suspend length and strength of the clavicle, the exten- 



itself from some projecting part. sion of all the bones of the anterior extremities, 



The pelvis is remarkably strait, rather elon- all admirably tend to fulfil their obvious end. 



gated, somewhat wider inferiorly. The ilia The existence of a tail for the support and 



are narrow and elongated ; the ischia in several extension of the interfemoral membrane, which 



species, instead of receding from each other, is found in the insectivorous Bats, compared 



approach so that their tuberosities touch each with its absence or comparative inefficiency in 



other, and in some instances come in contact many of the frugivorous, also points out an 



with the coccygeal bones. In some species of interesting relation to the different habits of the 



Pteropus, the anterior portion of the ossa pubis, two groups, the former structure being calcu- 



instead of meeting at the median line, recede lated to afford a powerful and effective rudder 



more or less from each other, and the space is in guiding their rapid and varying evolutions 



filled by ligament. In some species there is a in the pursuit of their insect food, 



sexual difference in this respect; the two pubic The general nervous system in the Cheiro- 



bones being in contact in the male and sepa- ptera does not exhibit any very remarkable 



rated in the female. peculiarity, but some of the organs of sense 



The sacrum and the ilia are connected by require a particular notice. 



absolute bony union at an early period. The Organs of the Senses. The organ of vision 



femur is of moderate length, slender and cy- is principally remarkable for its diminutive 



lindrical. It is turned outwards and upwards, size. The eye in many of the insectivorous 



so that the side which is usually anterior is group, in which the external ear is very largely 



directed nearly backwards. The tibia offers developed, is placed within the margin of the 



no peculiarity which requires particular notice, auricle and almost concealed by hair. In the 



The fibula is exceedingly small, slender, frugivorous group, on the other hand, it is 



pointed towards its femoral extremity, and has of the usual proportional size. The organ 



this singular peculiarity, that it does not rise of hearing, on the contrary, though in the 



to the head of the tibia. In other cases where latter forms not more developed than in most 



this bone is defective, it is at its inferior ex- other quadrupeds, in the former seems to take 



tremity, but in the present case it is the supe- the place of the diminutive organ of vision, 



rior portion which is wanting. As the femora being greatly extended both in its external and 



are directed outwards, the leg-bones are in internal organization. The external ear in 



some measure turned round, so that the fibula Pteropus is of the usual form and dimensions, 



are at the inner side of the tibia and a little and the eminences are not in any respect extra- 



behind them. ordinary : but in most of the insectivorous Bats 



The foot of the Cheiroptera does not ex- the conch of the ear is enormously large ; in 



hibit the same deviation from the normal many species being considerably larger and 



structure which we have seen in the hand. On longer than the head, and in the common long- 



the contrary, it is not extraordinarily developed, eared Bat of this country, Plecotus auritus, it 



and the different parts of which it is composed is nearly as long as the body. The tragus is 



are in the usual relative proportions. proportionally larger than in any other animals ; 



