16 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 



Another stage is represented by the Old World leaf-nosed groups, 

 the Nycteridse, Megadermida?, Rhinolophidse, and Hipposideridse. 

 In the first two of these the shoulder joint is still single, and the 

 shaft of the humerus shows a slight though evident sigmoid flexure; 

 the trochin and trochiter are as in the Emballonuridae, neither rising 

 distinctly above head. In the Rhinolophidse and Hipposideridte 

 the shaft of the humerus is nearly straight, with merely a slight 

 upward curve in distal third, while the trochiter has increased in 

 length sufficiently to exceed the head slightly and to form a definite 

 secondary articulation with the scapula by a surface about half as 

 large as glenoid fossa. In dze the trochiter is still distinctly ex- 

 ceeded by the trochin, which, however, barely rises above head. At 

 its distal extremity the humerus in all four families is peculiar in 

 the lengthened epitrochlea, bearing near middle a well-developed peg- 

 like process, and the very conspicuous displacement outward of the 

 capitellum and consequent widening of the entire distal region. This 

 displacement is greatest in 'the Megadermidse, where the articular 

 surface is almost wholly exterior to the axis, and the width of the 

 distal extremity is nearly one- fourth length of humerus. In the 

 Nycteridse the displacement is rather less, though the proportion 

 of width of extremity to length of bone remains about the same. 

 In the Rhinolophidse and Hipposideridse it is still less, and the 

 proportion of width to length is normal — that is, about as one to six. 

 The displacement of the articular surface remains very evident, and 

 the epitrochlea and its spinous process are of the same character as 

 in the Nycteridse and Megadermidse, though less elongated. 



In the American leaf -nosed bats the shoulder joint is essentially 

 like that of the Rhinolophidse and Hipposideridse, except that in the 

 Chilonycterinse the trochiter is so shortened as to form no articulation 

 with the scapula. In this subfamily the shaft of the humerus has a 

 slight single curvature, while in the others the bend is often, though 

 not invariably, double. Throughout the family the capitellum is 

 slightly displaced outward and the epitrochlea is small or moderately 

 developed, the spinous process, when present, at its distal extremity. 

 A similar type of humerus occurs in the Desmodontidse, but both 

 trochiter and trochin rise somewhat higher beyond head. 



The Natalidse, Furipteridse, Thyropteridse, and Myzopodidse agree 

 with each other in the form of the humerus. This differs from the 

 Phyllostomine type merely in the somewhat enlarged trochiter, which 

 now about equals the trochin in size and slightly exceeds it in height ; 

 distal extremity as in the Phyllostomidse ; flexure single or faintly 

 double. 



From the last type as best shown in the Thyropteridse to the highly 

 specialized form characteristic of the Vespertiliohidse, Mystacopidse, 

 and Molossidse the transition is rather abrupt. In these families 



