110 



MR. F, E. BEDDARD ON THE 



[May 17, 



vertebrfe ; but each intercostal bifurcates close to the parietes and 

 supplies but a single intervertebral area. The arrangement in 

 this region of the body in fact is precisely like that figiu-ed by 

 Jacquart * for Python sebce, and which I can confirm from my own 

 dissections of the same serpent. In Python sebce, however, this 

 arrangement appears to persist throughout the whole body. In 

 Eryx, on the other hand, a little way back, a third mode of 

 arrangement of the intercostal arteries occurs. The point of 

 bifiu'cation of the single intercostal advances higher up its stem 

 (rt in text-fig. 20) until (5) a right and left intercostal is established 

 arising separately from the aorta. A further dififerentiation is 

 sho\vn in the ciise of the intercost;\ls lettered c and d in the 

 figiu-e referred to. It will be observed that in c the left intercostal 

 is much thicker than its fellow and than most of the neighbouring 

 intercostals, while in d the vessel has become single owing to the 

 complete disappearance of its fellow. These facts indicate the way 

 in which the irregular intercostal arteries (sometimes right and 



Text-fig. 20. 



'c d '(r a 



Part of intercostal arterial system of I^ryx jandtis. 



Ao., aorta : a, h, c, d, intercostal arteries ; C.v.r., C.v.l., rigbt and left posterior 

 cardinals ; G-., gastric arter3- ; £., end of liver ; S.mes., superior mesenteric 

 artery. 



sometimes left and at unequal distances) of more modified snakes 

 have been formed. Oblitei-ate in the accompanying drawing 

 (text-fig. 20) the finer intercostals and leave only those of 

 magnified calibre, and the result would be a reproduction of the 

 intercostal system in many Colubrine Snakes. This double series 

 of intercostal vessels in Eryx has its counterpart in Eunectes 

 murinus. In the Anaconda I find both intercostals arising singly 

 which run for varying distances along the median dorsal line 

 giving ofi" paired branches to the parietes, and regularly paired 

 intercostals arising separately from the dorsal vessel It is 

 important to notice the agreement in these particulars between 

 Eryx and Eunectes and the difierence from Python, since the two 

 former belong to the subfamily Boince, and the latter, natiu-ally, 

 to the subfamily Pythonince. It is difficult to say which of the 



* Ann. Sci, Nat. (i) iv. p. 321. 



