508 



Bulletin American Museum of Natural History. [Vol. XXXVII, 



of voice. In the howling monkey (Alouatta), famous for its far-sounding 

 cries, the hyoid is transformed into a resonating apparatus, but in the males 

 of Hysignathus monstrosus the importance of the vocal efforts consists not 

 so much in the strength of their noise as in the continuity of their produc- 

 tion. We find instead of a fixed ossified reverberating organ, as in Alouatta, 

 a pair of air-sacs inflated at will and a tremendous enlargement of the larynx 

 and vocal cords. The sound produced can hardly have any other purpose 

 than to attract the females. 



The drawings (Figs. 19 and 20), make it perfectly plain that the larynx, 

 as Matschie says, "is nearly equal in length to one half of the vertebral 

 column/ ' and actually fills the greater part of the thoracic cavity, crowding 

 the heart and lungs back and sideways until the posterior end of the cricoid 

 cartilage is practically in contact with the diaphragm. The trachea is 

 wide, but folded upward on the posterior surface of the larynx. This 

 extreme development of the larynx is simply the result of the enlargement 

 of its usual elements, especially the thyroid, arytenoid, and cricoid car- 

 tilages, which have undergone extensive ossification. The vocal cords 

 are extremely broad, and it is our belief that all these modifications have 

 to do mainly with the voice, although Dobson held that the arrangement 

 of the pharynx, hyoids, and their muscles was admirably suited for sucking 

 out the soft interior of fruits. 



The whole abdominal cavity is relatively restricted in size. As might 

 be expected from the nature of the food, which consists of fruit-juices, the 

 stomach is rather small, bent upon itself, with its inner lining deeply folded, 

 while the intestine is slender and much convoluted. In both these speci- 

 mens the alimentary tract was empty. 



4. Ephomophorus anurus Heuglin. 



Plate XLIV, Fig. 1, and Plates XLVI and XLVIL 



Beyond the northern edge of the forest, the common representative of 

 the family is this medium-sized fruit-bat, with a rudimentary tail, never 

 more than one-third of an inch (6 mm.) in length, right below the inter- 

 femoral membrane. The uniform brown color of the back looks more or 

 less faded in the different individuals, and they are still paler on the ven- 

 tral side, an ill-defined whitish abdominal patch being especially apparent 

 in adult males. These, of course, are easily distinguished from the females 

 by the curious white epaulets and sometimes show a darker band across 

 the breast. An adult male measures 5.75 inches (145 mm.) in length and 



