470 MR. F. E. BEDDARD ON THE [NoV. 28, 



after giving off at any rate one intei'costal twig, divides into two 

 slender trunks diverging right and left. Each of these separates 

 from itself immediately after its own origin a vessel which 

 rapidly plunges into the thickness of the body-wall in the middle 

 line, and which represents on either side the anterior vertebral 

 arteries of other Lizards. In spite of the limbless character of 

 this OpMsatijTus, the subclavians are still more distinctly re- 

 cognisable as such than they are in AmpMsbcena. 



The left aorta gives off several vessels to the oesophagus before 

 joining the right aorta, but no intei-costals. On the other hand, 

 the right aorta gives off several intercostals before joining the 

 left. Rathke mentions oesophageal arteries as arising from the 

 right aorta. 



The carotid artery does not pass up the neck alongside of 

 the trachea. But the windpipe is, as in other Lacertilia, accom- 

 panied by an arteiy. This artery, however, in Op>hisaurus is 

 only to be seen on the right side of the trachea ; on the left there 

 is at most a rudiment of the same. It gives off branches to the 

 th}T?oid which correspond to those given off on the left side by 

 the carotid arch before it gives off the carotid artery. This 

 tracheal arteiy arises, as do the corresponding pair in Hatteria, 

 &c., from the pulmonary artery. In Op)Msa%<jrus it is accom.- 

 panied by a vein of larger calibre than itself, which runs up the 

 neck in close contact with it and again only on the right side. 

 On the left I could discover no traces of a corresponding vein. 

 This vein joins the ante]:'ior cava. The asymmetry in this part 

 of the arterial system is noteworthy, for the reason that it is the 

 only part of the arterial system which shows, in correspondence 

 with the snake-like habit of body, any traces of an asymmetry. 



The dorsal aorta gives off ventrally a regular paired series of 

 intercostals, which fail apparently nowhere and are even and 

 regularly paired throughout. 



(Esophageal and Gastric Arteries. — A striking feature of this 

 Lizard as compared with many is the very large number of 

 trunks arising from the aorta which supply the oesophagus 

 and stomach. There are two oi' three oesophageal vessels arising 

 from the left aorta before it joins the right. After the junction 

 there are seven small arteries still supplying the oesophagus. 

 Of these, which are not mentioned by Rathke, the first four 

 arise from the aorta itself. After these come three trunks, 

 which arise not from the actxial aortic trunk but from the inter- 

 costal vessel of the left side. All of the oesophageal arteries 

 are very small and at the same time very convoluted in their 

 course. Following them are five gastric trunks, which are all of 

 greater calibre than the oesophageal vessels. The last three of 

 these are particularly important. A considerable gap separates 

 these gastric vessels from the three chief arteries which end upon 

 the walls of the intestinal canal. Hochstetter has figured three 

 variations in point of origin of these threearteries. In the individual 

 dissected by myself I found one of these three arr-angements to 



