34 MR. F. E. BEDDARD ON THE [Jan. 16, 



important also to note that the intercostal arteries arise from the 

 aorta as single trunks and bifurcate later. The arrangement of 

 these arteries, in fact, is precisely as in Python, as figured by 

 Jacquart. 



Among the Lacertilia it is very general, if not universal, for 

 the mesenteries to contain muscular strands, which in the case of 

 the dorsal mesentery arise from the vertebral musculature and are 

 often inserted on to viscera. These bands of muscle are made up 

 in all cases where tliey have been examined of unstriped fibres. 

 I find in Ilysia a structure which is to be regarded as the equivalent 

 of these bands of muscle in the Lacertilia. This consists of a single 

 band of fibres of about the same calibre as one of the larger 

 arteries — for which indeed, or for a vein, I at first mistook 

 it. The nacreous glitter, however, of the strand shows its 

 muscular natui^e, which appearance was confirmed by microscopic 

 examination. The fibres of which it is composed are plain fibres. 

 This band of muscle arises from the centra of two vertebree by 

 strands from each near to the posterior end of the liver. It runs 

 obliquely forwards, and ends in an attachment to the upper surface 

 of the liver. It avoids the alimentary canal, passing to the right 

 of that tube. The existence of only this one straight band of 

 fibres of unvarying calibre throughout is different in detail from 

 what is found among the Lacertilia. 



From this necessarily imperfect survey of the anatomy of 

 Ilysia, it is possible to abstract two characters in which this genus, 

 placed in a Family of its own, resembles the Boidse, and one other 

 in which it departs from the structure of that group. 



Ilysia agrees with the Boidse in the following points : — 



(1) In the regularity and paired character of the intercostal 



arteries. 



(2) In the fact that each kidney is supplied by a single renal 



artery. 



On the other hand, Ilysia differs from the Boidte (excepting 

 Ungalia*) chiefly in the fact that the lungs are not normal paired 

 structures but that one is rudimentary. 



The other features which I have been able to note in this 

 survey of certain points in the anatomy of this genus are, in the 

 present state of our knowledge, indecisive of the afiinities of the 

 genus. 



(4) Tlie Structure of the Young Bitis nasicornis, vnih 

 Notes on other Vipers. 



A considerable number of young Vipers of this species were 

 born in the Gardens in November last, some of which were alive, 

 whilst some had been born dead. I examined several of the latter. 

 The young snakes were enveloped in the amnion, and the othei- 



* See Cope, "On the Lungs of the Opliidia," Proc. Amer. Phil. Soc. xxiii. 1884, 

 p. 220. 



