16 BULLETIN 57, UNITED STATES NATIONAL MUSEUM. 
Another stage is represented by the Old World leaf -nosed groups, 
tlie Nycteridae, Megadermidae, Rhinolophidae, and Hipposideridae. 
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 Rhinolophidae and Hipposideridae 
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 ; ize 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 Megadermidae, where the articular 
surface is almost wholly exterior to the axis, and the width of the 
distal extremity is nearly one-fourtli length of humerus. In the 
Nycteridae the displacement is rather less, though the proportion 
of width of extremity to length of bone remains about the same. 
In the Rhinolophidae and Hipposideridae 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 Nycteridae and Megadermidae, though less elongated. 
In the American leaf-nosed bats the shoulder joint is essentially 
like that of the Rhinolophidae and Hipposideridae, except that in the 
Cliilonycterinae 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 Desmodontidae, but both 
trochiter and trochin rise somewhat higher beyond head. 
The Natalidae, Furipteridae, Thvropteridae, and Myzopodidae 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 Phyllostomidae ; flexure single or faintly 
double. 
From the last type as best shown in the Thyropteridae to the highly 
specialized form characteristic of the Vespertilionidae, Mystacopidae, 
and Molossidae the transition is rather abrupt. In these families 
