108 MR. F. E. BEDDARD ON THE [May 17, 



a primitive character. There is no a priori objection to deriving 

 the Ophidia from some Lacertilian form in which the characteristic 

 lacertilian " tag " to the heart was absent. In the genus Varanus, 

 for example, the gubernaculum is absent, as others as well as 

 I myself have observed ; and it may be pointed out that the 

 Ophidia might well have been derived from some form in which, 

 as in Varanus, the neck was long, the lungs firmly bound down 

 to the dorsal parietes, the trachea or bronchi continued for a 

 considerable distance through the lung, and the ui'inary bladder 

 absent. 



The fact that in Eryx the right and left aortic arches are equal 

 in size at their junction to form the unpaired dorsal aorta seems 

 to me to be undoubtedly a primitive feature. I may furthermore 

 observe that this feature is figured * by Dr. Gadow as charac- 

 teristic of PelophUus (Boa) niadagascariensis. Apparently, how- 

 ever, Python hivittatus has unequal right and left aortse t. In 

 other serpents it is common for the right aortic arch to be 

 smaller than the left, and this is carried so far in Zamenis Jlagelli- 

 formis as to give the impression that the right aorta is a mere 

 inconspicuous forwardly running bi-anch of the left +. 



§ Intercostal Arte7-ies. 



The intercostal arteries in Eryx jaculus show some interesting 

 features, which are partly indicated in the accompanying di-awing 

 (text-fig. 19, p. 109). In the anterior region of the body the 

 arteries in question aiise from the left aorta immediately after it 

 has parted company with the anterior vertebral. Anteriorly to this 

 point some arise from the left aorta, but that region of the body 

 is supplied from the vertebral artery. The intei'costal artei-ies 

 which arise from the right aorta and from the fii-st part of the 

 conjoined aortte are single trunks given off at irregular intervals 

 not corresponding to the individual vertebra. They join above, 

 however, to form a continuous and slender dorsal artery which 

 may be tei^med the posterior vertebi-al artery {P. v.) ; from this 

 arise at regular intervals the paired intercostals. 



After the end of this vertebral artery the aorta continues to 

 give off the dorsal intercostals Avhich, when they reach the median 

 dorsal line, run along it for a shoi't distance anteriorly and 

 posteriorly, giving off as before paired branches to the intervertebral 

 regions. But there is no formation here of a continuous 

 longitudinal trunk I'unning over more than three or four vertebi-a?. 

 So far the arrangement is precisely such as I have lately described 

 in another Bold, viz. Python sjnlotes^. But whereas in the last 



* Bronn's Klasseii uud Ordmmgen des Thier-Reiclis, Bd. vi. Abtli. iii. pi. cxxxv. 

 fig. 1. 



t Loc. cit. pi. xxxiv. fig. 2. The figure is copied from Fritsch. 



X Beddard, "Contributions to our Knowledge of the Vascular System in the 

 Ophidia," P. Z. S. 1904, vol. i. p. 338. 



§ " Contributions to our Knowledge of the Circulatory System in the Ophidia," 

 P. Z.S. 190i, vol. i. p. 3(32. 



