A MONOGRAPH OF THE BATS OF NORTH AMERICA. 17 



orus the bouc extends dowii\v;ird posteriorly and at the sides so as 

 to conceal the lower opening of the canal for the vertebral canal. The 

 upper border of the conjoined laininic is boldly rugose. In ArtlheuH^ a 

 member of a group in the Xew World analogous to the foregoing, the 

 atlas is greatly reduced in the proportions of the lamiujc and the trans- 

 verse process, the lower opening of the canal for the vertebral canal is 

 exposed on the posterior asi)e('t of the bone, while the upper border of 

 the conjoined lamiua3 is scarcely rugose. In the vespertilionines, molos- 

 sines, and phyllostomines minor peculiarities distinguish the atlas. 

 These are given in the diagnosis of genera and species. In a general 

 way it may be said that the pteropines are broadly separated from all 

 the other bats by the characters presented by this bone. In Pteropus 

 and Epomophonis the axis possesses a large neural spine which almost 

 equals the length of the body inclusive of the cylindroid odontoid proc- 

 ess. In Artihem the spine is but one-half the length of the bod}^, inclu- 

 sive of the tubercle-like odontoid process. The remaining portion of the 

 cervical is curved more or less antero posteriorly. This is less marked 

 in the i)teropine and phyllostomine genera than in the vespertilionine, 

 where the curve is so great as to bring the occiput almost to the first 

 dorsal vertebra. The sacrum, at its upper portion, exhibits a compressed 

 projecting ventral surface. The spinous processes are flat, distinct, and 

 increase in sjze from above dowuAvard in molossines and Atalaplia^ but 

 they are low and confluent in many forms as in the i:)teropines. The 

 first coccygeal vertebra in tailed forms is large and resembles those of 

 the sacrum. The caudal vcrtehra' below this are cylindroid. They 

 vary greatly in length, especially at the beginning of the series. 



Eibs. — The first and second ribs are flat and broad (coalescent in 

 Natalus and Hipposideros), but as a rule have a wide interspace. The 

 other interspaces are also well defined in Pteropidie, but are often 

 narrow, and in ^atalus and Hipposideros are practically obliterated. 

 The costal cartilages are relatively inelastic and are disposed to become 

 early calcified. Indeed, the entire chest is rigid, and the ribs often 

 become anchylosed to the spine, and in some forms, as in old individ- 

 uals of YespertUlo murinus, the contiguous ribs to each other. Hence 

 the respiratory movements are for the most part performed by the 

 diaphragm and the flank muscles. 



Sternum. — The prosternum is broad and massive, while both the 

 mesosteruum and metasternum are narrowed. The prosternum sends a 

 conspicuous process forward into the neck (as in many terrestrial mam- 

 mals) in molossines; all the others are without this process. The first 

 joint is usually conspicuously keeled, and in Pteropida? this keel is 

 divided by a deep notch. The mesosteruum in the same family is also 

 keeled its entire length, but in the other groups it is barely ridged or 

 smooth. 



Anterior Umh. — The clavicle is ])resent in all bats. It is firmly at- 

 tached at both the acromial and the sternal end. The last named 

 441—1^0. 43 2 



