1908.] 



AYE-AYE AND OTHER LEMURS. 



699 



In another specimen, however — and this is important as showing 

 the variation of these structnres — the first intercostal was single, 

 the next two were paired but the left-hand arteriole was smaller 

 than, and lay behind, the right. Then followed a strictly joaired 

 and equisized couple rather far aj^art, and after this another jiair 

 closer together. In a Beaver {Castor canadensis) the intercostal 

 series commenced with a single vessel on the left side ; then 

 followed three pairs the orifices of each pair getting closer 



Text-fiff. 152. 



Right-liand figure. — The commencement of the aorta of Chiromi/s cut open to 



show origin of intercostals. 



a. Commencement of descending aorta. D. Position of diaphragm. 



Left-hand figure. — Azj'gos {As.) of Chiromt/s. 



Ao. Aorta with some of intercostal branches indicated. 



together, then a single median intercostal, followed by three 

 pairs, and these again by a single median artery. After this 

 point the artery traversed the diaphragm, and the intercostals 

 behind the diaphragm arose singly, and were median in position. 

 In a Chinchilla {Chinchilla lanigera) the first intercostal was 

 median and unpaired. Then followed a single vessel on the right 

 side and then two paks. The remaining intercostals were median 



