INTRODUCTION. Xlll 



bases lying inwards, their apices very acute. The anterior cusp 

 is wider and somewhat liigher than the posterior. 



The vertebral column is remarlcable for the absence of any 

 prominent processes. The cervical vcrtebriE are little more than 

 slender rings of bones surrounding a spinal marrow of unusual 

 width. The dorsal are also very uniform in appearance, each 

 bone having its sides furnished with a slightly elevated tubercle. 

 The iHbs attached to them are relatively broad, very long, and 

 much curved, thus giving the thorax a somewhat compressed 

 appearance. The first rib is remarkable for its extreme breadth, 

 especially at the point where it articulates with the sternum, 

 being here twice the width of the clavicle. The sternum is 

 of great strength. The manubrium is markedly crested, broad 

 and flat at base whence two blunt, obtuse alaa spring from either 

 side to articulate with the clavicle and first rib. The gladiolus 

 and xyphus are large and robust ; the latter has upon its inferior 

 extremity an expanded cartilaginous piece, which is continuous 

 with the linea alba. The object of this excessive development 

 of the sternum is evident : the immense power employed in 

 the maintenance of flight necessitating the presence of strong 

 osseous points for attachment of the muscles. The clavicle is 

 long, much arched, and slightly flattened from before backwards. 

 The scapula is of a sub-rhomboid shape. At the upper third 

 of its dorsal surface the dorsal spine runs obliquely forwards 

 and terminates in the large acromion. The coracoid process is 

 also conspicuous, and projects at right angles from the scapula 

 parallel with a similar process from the internal superior angle 

 of the shoulder blade. The humerus is long, cylindrical ; head 

 small, scarcely longer than shaft ; two processes before and behind 

 the articulation are observed for the insertion of the scapular 

 muscles. The inferior extremity has but one articular facet. 

 The forearm consists of the radius alone, the ulna being entirely 

 absent or confined to a mere rudiment attached to the upper 

 posterior part of the radius. The radius is slightly arched, 

 much larger than humerus, and like it without any process. The 

 carpus is composed of 6 bones, of which the largest supports 

 the radius. The bones of the metacarpus are greatly developed 

 in length, constituting the bony frame-work upon which the wing 

 membranes are stretched. The thumb has two joints, the terminal 

 one of which is surrounded by a claw, the others having generally 



