1904.] CIRCULATORY SYSTEM IX THE OPHIDIA. oH^ 



aorta ami vertebral artery, but a special lympli-tube enslieathes 

 the outgoing intercostal artery, and beside it another lymph-tube 

 (see text-fig. 70, p. 352) which does not contain an artery, but 

 whose presence possibly indicates the former existence of such an 

 artery. Traced anteriorly, the vertebral artery gives off a branch 

 to every intervertebral space. iSome of these, however, are 

 excessively fine and might readily be missed. Tliere are 

 fourteen, however, which are stout arteries and could not be 

 missed, which lie between the origin of the anterior vertebral 

 and the point at which it disappears into the thickness of the 

 parietes. It is interesting to note that none of the intercostal 

 branches seem to be really missing ; tiiey are simply unequally 

 developed. All these arteries are exactly median in their point 

 of enti-ance into the parietes, and a clean-cut circular orifice in 

 the parietes considerably larger than the artery permits its 

 passage. The right aortic arch gives off two intercostals before 

 it joins the larger left aortic arch. As is the rule in the Ophidia, 

 the intercostals in the anterior region of the "thorax" are much 

 less numerous than they are posteriorly. But here there are not 

 indications, as there are in the cervical region, of missing inter- 

 costals. This suggests the length of the trunk is an older feature 

 of the Ophidia than the length of the neck. 



This snake differs from some others in the fact that the bulk 

 of the intercostal arteries beginning quite anteriorly divide near 

 to the dorsal middle line, so that the entrance into the pai-ietes 

 is on both sides of the vertebra. The very first of the inter- 

 costals, and after two others which are single and enter on the 

 left side, is another which bifurcates ; thereafter follows a series 

 which regularly bifurcates. Further back the usual and irregular 

 alternation of the arteries is to be noted. As this more or less 

 regular bifurcation of the anterior intercostal arteries occurs in 

 both specimens, it may fairly be regarded as typical of the species. 



Gastric Arteries. — The gastric arterial system in this snake 

 shows certain broad differences from that of Coluber melanoleucus. 

 It is possible in the first place to distinguish two series of gastric 

 arteries, small and large. This is not simply a question of larger 

 posterior and smaller anterior gastric ai'teries, such as occur in 

 Coluber. In Coronella getida there ai-e a few large arteries which 

 vary somewhat in size among themselves, and a host of minute 

 arteries of almost microscopic size. There is no series of tran- 

 sitions between the minute and the large arteries ; the latter lie 

 among the former. The minute arteries form a complex network 

 in the mesentery of the stomach, though with very large meshes, 

 and end upon the surface of the stomach. This network appears 

 to join the trunks of the larger gastric arches. 



Of the large gastric arteries there are five, of which the first 

 and the last are not purely gastric but also supply other organs. 



The first gastric artery arises just at the junction of the 

 oesophagus and stomach, and just at the end of the liver. It is 

 much larger than the preceding hepatic arteries, so that there is 



Proc. Zool. Soc— 1904, Vol. I. No. XXIII. 23 



