18 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



effects au important articulation with the cartilage of the first rib and 

 in the sterno-claviculo-costal joint ; in Molossi, at least, it is of enormous 

 strength. The .-icapida, as in other claviculate forms, with few excep- 

 tions, in which the large anterior extremity is not supported on the 

 ground, possesses an infraspinatus fossa very much larger than the 

 supraspinatus. The bone lies well up on the side of the ueck in the 

 forms in which the cervical series of vertebra^ is bent forward. Excel- 

 lent characters are yielded by thecoracoid process. It is always longand 

 slender, simple, and gently curved in various arcs in Pteropida^, Ivhi- 

 nolophida-, Emballonurida?, and Phyllostomidte, but bifid in most 

 Vespertilionida'. It is interesting to find the genus VespertiHo aber- 

 rant in this respect, the process being simple and curved quite as in 

 the larger groups first named. The posterior tubercle is prolonged to 

 form an obli(iue posteriorly-directed process in Lasionycteris, and the 

 molossines Atalapha and ChaUnolohus. 



With the excei)tion of the tuberosities of the humerus no check 

 processes exist anywliere in the bones of the limbs, thus presenting 

 marked contrasts witli the limbs of birds. The trochlear end of the 

 humerus yields in tlie shape and direction of the epitrochlea valuable 

 characters. This process conforms to the terrestrial type, i. e., it is 

 transversely inclined in pteropiues and the genus Saccopteryx; is de- 

 flected downward parallel or nearly so to the shaft in pljyllostomines 

 and molossines, but is absent in vesi)ertiliouines. In vespertilionines 

 again the articular surface is axial, /. r., is in the middle line of the 

 humerus, but in phyllostomines it is thrown well off to the outer side. 

 Narrow- winged forms, as the molossines and the genus Atalaphg,^ exhibit 

 large tubercles on the humerus and wide trochlear surfaces. Thus 

 these characters harmonize with rapid flight. On the other hand, the 

 forms with smaller tubercles and narrow, poorly defined trochlear sur- 

 faces have broad wings and presumably slow flight. 



The radiitti constitutes the main support of the forearm and presents 

 few variations from a single type. As a rule it is nearly straight, but 

 is much bent in Hipposideros. It is always obliquely grooved by the 

 tendon of the extensor ossi metacarpi jjollicis. The size of the large, 

 deep fossa for the insertion of the biceps flexor is variable. Since the 

 ulna does not enter into the composition of the anterior arc of the 

 trochlea, and its place is here taken by the radius in addition to the 

 work this bone does in articulating with the humerus at its outer half, 

 it is easily seen that the radius is provided with two facets at its prox- 

 imal end, and that the main ridge on the distal articular surface of the 

 humerus fits in between these two radial facets. 80 far as the degree 

 of invasion of the radius into the trochlea has been noted it appears to 

 correlate with the degree of activity of the prone form in scurrying. 

 It is thus marked in Chelromeles and Molossus, and is small in 

 Kerivoula. 



The ulna is more inconstant in form than the radius ; in all it is in- 



