16 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



most part smooth externally, as in Canis, while in the fauna generally 

 it is short, as in Felis, and the outer wall is often elevated. 



The hard palate maybe either in tlie main axis of the skull, as in lAost 

 forms, or deflected ujiward and forward. The characters furnished by 

 the pterygoid processes, the palatal plates, are here as useful as in 

 other mammalian groups. The premaxillie are rarely firmly united to 

 one another. When they are so united, as in Phyllostomidfe and Mo- 

 lossi, the median incisors are disposed to be contiguous. When they are 

 not united, a large median interspace separates them and is continuous 

 with the vacuity which in other mammals represent the incisorial for- 

 amen. The presence or absence of the sphenopalatine foramen is used 

 in some groups, as Molossi and in Plecoti, in separating genera. The 

 disposition of the turbinals is also of interest, the j^eculiarities of the 

 arrangement being definitive of the families as established on other- 

 structural characters. If in mammals generally an outer and an inner 

 turbinal group is recognized, then in the bats we have a median lamina 

 which bears upon its inner surface one or more scrolls (endoturbinals), 

 and an outer lamina with uuich simpler accessories (ectoturbinals). 

 The simplest arrangement of the turbinals is seen in the N'ycterid;!' and 

 Ehinolophida^, the most complex in Pteropidse. In Natalus alone is 

 the ectoturbinal rudimental or absent. (Bull. Mus. Comi). Zool., Feb., 

 1880.) 



In addition to the peculiarities of the masseteric impression on the 

 lower jaw, already noticed, characters are furnished in the height of tlie 

 coronoid process and the degree of deflection as well as the size and 

 shape of the angle. The post-sympliysal sjiine which is conspicuous 

 in some extinct forms has not been seen by me in any of the extant 

 forms {Promops perhaps excepted), and I have examined most of the 

 genera of the order. 



The shortening of the face, 2)ari passu, with reduction of teeth, is seen 

 in Carnivora. The tendency is seen in Yesptrugo, and in bats gen- 

 erally. In Vespertilio the shortening of face is accompanied by dis- 

 placement inward of the premolars. In a mechanical sense it amounts 

 to the same as reduction in number. In pteropine bats a remarkable 

 persistence of facial length remains, while the disposition to reduction 

 is evident. One may conclude from the instance last named that the 

 shortening of face and reduction of teeth are independent. The same 

 is true of the Ungulata. 



In AtaUtplia the lower jaw closes in front of the upper. The lower 

 canines articulate with the anterior surfaces of the upper laterals their 

 entire length. The upper canines are free, i. e., do not articulate with 

 anything. 



Yertehral column. — The vertebral column is without large processes 

 other than the Inemopoi^hyses which are well developed in the cervical 

 region. 



The atlas is broadest in Pteropidoe. In both Pteropus and Epomoph- 



