518 ZOOLOGY 



SECT. 



The pectoral arch also varies a good deal in the different 

 families of the Insectivora. In the true Moles and their allies 

 there is a remarkable bone of cuboid shape articulating ventrally 

 with the presternum and dorsally with the humerus, and only 

 connected by a ligamentous band with the scapula. Its mode of 

 formation from a mass of cartilage to the anterior face of which 

 the clavicle, formed as usual in membrane, becomes applied, proves 

 that this bone represents a pro-coracoid as well as a clavicle. In 

 the rest this bone is not developed, and the clavicle is a distinct, 

 long and slender bone, but vestiges of the inner or ventral ends of 

 the coracoid and pro-coracoid may be recognisable. Sometimes 

 the ' mesoscapular segment' 1 is represented by a distinct bone 

 intervening between the outer end of the clavicle proper and the 

 acromion process. 



The humerus usually has a supracondylar foramen. In the 

 Moles this is absent, and the humerus is remarkable in other 

 respects, being short, greatly expanded at the extremities, with a 

 prominent deltoid ridge, and with two synovial articular surfaces 

 at the proximal end, one for the glenoid cavity of the scapula, the 

 other for the coraco-clavicle. The radius and" ulna are completely 

 developed and usually distinct, but are sometimes fused distally. 

 In the carpus the scaphoid and lunar sometimes coalesce, sometimes 

 remain distinct ; an os centrale is usually present. In the Moles 

 the manus is extremely broad, the breadth being increased by the 

 presence of a large curved radial sesamoid. 



In the pelvis the symphysis pubis is sometimes elongated, 

 sometimes short, sometimes absent, the pubes remaining separated 

 by a wide median ventral cleft. A third trochanter is sometimes 

 represented by a ridge. The fibula usually, though not always, 

 fuses distally with the tibia. 



Skeleton of the Chiroptera (Fig. 1105). The cervical region, 

 of the vertebral column is characterised by the absence of any 

 distinct neural spines, and the same holds good to a less extent of 

 the trunk vertebrae ; the transverse processes of the lumbar region 

 are also rudimentary. The tail varies in development: when it 

 is elongated the component vertebrae are long cylindrical centra 

 without processes. Sagittal and occipital crests are developed in 

 the skull of some species. The facial region is rather elongated 

 especially in the Megachiroptera (Fig. 1106). The post-orbital pro- 

 cesses of the frontal are present or absent : the zygoma is long and 

 slender: the malar is small and applied to the outer surface of 

 the zygoma. The long and narrow nasals are sometimes united :. 

 the pre-maxillae are small. The mandible has an angular process 

 in the Microchiroptera, not in the Megachiroptera. The segments; 

 of the sternum are sometimes distinct, sometimes united, the pre- 

 sternum has a mesial keel developed in co-ordination with the 

 great size of the pectoral muscles. The sternal ribs are ossified. 



