The arterial system of Ptyas mucosus (Linn.) reveals the following interesting features: (1) A prominent diverticulum given off from the inner antero‐dorsal edge of the left auricle. (2) Ridge‐like continuation of the median hanging valve of the sinus venosus lining the ventral edge of the opening of the right precaval vein. (3) Guarding of the opening of the pulmonary vein by a portion of the inter‐auricular septum abutting against it. (4) Presence of two longitudinal trunks on either side of the hepatic portal vein formed by the hepatic branches of the hepato‐oesophageal arteries, which, uniting with one another, form a peculiar arrangement looking almost like a looped chain. (5) A complete arterial circuit in the female formed by the combination of the genital, supra‐renal, and the anterior‐most renal arteries of either side. (6) Chain‐like arrangement formed by the alternate bifurcation and union of the posterior‐most part of the longitudinal fat‐body artery and also by its lateral branches, which unite with it here and there after giving off twigs to the fat bodies. (7) A pair of small arteries (or in some cases only one) called ‘arteria complexa’ which take their origin from the dorsal aorta opposite the openings of the iliac veins into the afferent renals. Copyright © 1934 Wiley‐Liss, Inc.