16 NORTH AMERICAN BATS — H. ALLEN. 



The at his is broadest hi Pteropiche. hi both Ptrropus and I'JpoinopTi- 

 <>rf(s the bone exttMuls downward posteriorly and at the sides so as 

 to eoneeal the h)wer «)i)eninjj;" of the canal for the vertebral canal. The 

 ui>])er border of the conjoined lamina' is boldly rii^(>se. In Artibeus, a 

 member of ai ,uroiip in the Now World analoi;'ous to the forei^oini;', the 

 athis is greatly reibiced in the i)roportions of the laminu> and the trans- 

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

 exposed on the posterior as])e('t of the l)one, while the npj)er border of 

 the conjoini'd lamina' is scarcely rugose. In the vesi)ertilionines, 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 i)teropines are broadly separated from all 

 tlie other bats by the characters presented by this bone. In Pteropiis 

 and Epo))K)i>Ji()n(s the axis possesses a larger neural spine which almost 

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

 cess. In Artibeus the spine is but one-half the length of the body 

 inclusive ofthetubcrcle-likc^ odontoid i)rocess. Theremainingportionof 

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

 in the pteropine and phyllostomine genera than in the vespertilionine 

 where the curve is so great as to bring the occi])ut almost to the tirst 

 dorsal vertebra. The sacrum, at its upper i)ortion, exhibits a compressed 

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

 increase in size from above downward in molossines and Atolapha, but 

 they are low and contlueut in many forms as in the pteropines. The 

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

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

 vary greatly in length, csi)ecially at the beginning of the series. 



Bibs. — The ribs are Hat, broatl, with wide intercostal spaces (coales- 

 eent in Xat(th(,'i and Hipposidi'ros for the region of the first and 

 second ribs). The other interspaces are also well defined in Pteropida', 

 but as a rule they are narrow, and in Xafalufi and Hippos id eras 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 ancliyl)sed to the si)iiie, and in some 

 iorms, as in old individuals of Vespvrtilio muriniis, the contiguous ribs 

 to each other. Hence the respiratory movements are for the most part 

 performed by the diai)hragm and the flank muscles. 



iStcrnio)!. — The sternum possesses a massive, broad prosternum and a 

 narrowed mesosternum and metasternum. The prosternum sends a 

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

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

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

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

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

 smooth. 



Auicrior li)ni>s. — The clavicle is present in all bats. It is firmly at- 

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



