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Show 1906.] ANATOMY OF THE OPHIDIA. 33 stomach is, as already mentioned, traversed by three thick folds, which show here and there an interesting trace of a reticular arrangement. There are occasional short blanches of the folds, which, although they do not reach another fold, indicate an approach towards, or a reminiscence of, a reticular arrangement. Towards the posterior end of the anterior part of the stomach the folds lose their importance and smaller folds between them appear. But the whole series of folds dies out upon a cushionlike elevation. Then follows the shorter posterior region of the stomach, which is entirely free from rugaB of any kind. The small intestine is short as compared with that of some other serpents. Not counting its windings, it measures in a straight line from the end of the stomach to the beginning of the large intestine 51 mm., or 2 inches. About half of this consists of a closely-folded section, which commences immediately after the circular valve separating the stomach from the intestine. Then follows a straight section, which just before its opening into the dilated commencement of the large intestine bends once or twice abruptly upon itself, thus constituting another shorter coiled region. The intestine is lined with fine wavy folds. The large intestine is also 51 m m . in length to the anus. Vascular System.-Though it is impossible to elucidate the arrangement of the vascular trunks in a spirit-preserved specimen in a thorough fashion, I have nevertheless been able to ascertain certain facts which are of importance from a systematic point of view. I have been able to follow the abdominal branches of the aorta, and find that the first hepatic branches are disposed as follows:-Thej^rs^ branch which arises supplies the stomach, and reaches that organ at about its middle. On a level with the gallbladder a second equally stout branch is given off which divides into two trunks: one of these runs forward and is gastric ; the other has a posterior course and is intestinal. The next branch of the aorta is that of the right testis; it is of course very slender. I did not discover the corresponding branch to the other testis. The next artery to arise is the right renal, which enters the kidney near to its anterior end. A rectal artery comes next and is followed by the left renal, which is also the only artery of this kidney and enters it near to its anterior end. Then follow three rectal cwteries. Intercostal Arteries.-In the arrangement of these arteries Ilysia plainly shows its affinities to the BoidaB. In the last-mentioned family * the intercostal arteries are paired structures, which is not the case with, at any rate, many Colubridae and YiperidaB. In Ilysia the same paired structure is plainly visible; furthermore, it is to be noted that the intercostal arteries are regular in their arrangement-that is, that they supply the intercostal spaces continuously, a pair of arteries corresponding to each vertebra. This is, of course, also a Boine character. It is * Jacquart, Ann. Sci. Nat. (4) iv.; and Beddard, P. Z. S. 1904, vol. i. p. 338, & P. Z. S. 1904, vol. ii. p. 108. PROC. ZOOL. Soc-1906, YOL. I. No. III. 3 |