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 bifm-cate later. The ai'iungement of 

 these arteries, in fact, is jjrecisely 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 insei'ted on to viscera. These bands of muscle are made up 

 in all cases where they have been examined of unstiiped fibi-es. 

 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 nature, 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 vertebras by 

 strands from each near to the posterior end of the liver. It I'uns 

 obliquely forwards, and ends in an attachment to the upper sui-face 

 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 difierent in detail from 

 what is found among the Lacei'tilia. 



From this necessarily impei'fect 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 Boida^, and one other 

 in Avhich it departs from the structure of that group. 



Ilysia agrees with the Boida? 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 difiers from the Boidse (excepting 

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

 structvares but that one is rudimenttiry. 



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 aflinities of the 

 genus. 



(4) 17ie Structure of the Yotmg Bitis nasicornis, tciik 

 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 lattei-. 

 The young snakes were enveloj^ed in the amnion, and the other 



* See Cope, "On the Lungs of the Ophidia," Proc. Amw. Phil. Soc. xxiii. 1894, 

 1 . 220. 



