Fig. 34 represents a horizontal section through the gastric ostium at the level of the arrow _a-b_ in Fig. 32, or arrow _c-d_ in Fig. 33. The reference numbers 5, 6 and 7, 8 denote similar points in the two figures 33 and 34. Fig. 32 as referred to Fig. 34 is through the arrow _e-f_; Fig. 33 is through the arrow _c-d_. In the series of cross-sections, Fig. 9 is taken at a level a little below that of Fig. 34, and passes through the basal part of the valve (_vg_).
(b) _Marginal Pockets._ The part of the peripheral portion of the gastro-vascular system in each quadrant which is called the stomach pocket extends downwards as far as the sensory niche. Here by the coming together of the walls of the exumbrella and subumbrella the space between them is obliterated (Fig. 15) in the immediate perradius. From the sensory niche downward to the margin each stomach pocket is thus divided into two smaller pouches, the marginal pockets (_mp_). In each side of the Cubomedusan cube there are, then, in Charybdea two marginal pockets; or in all eight, a characteristic of the family Charybdeidæ. The marginal pockets as the name implies extend downwards to the bell margin, and are continued into the velarium as the velar canals. Of these (Fig. 3) there are two from each marginal pocket, or sixteen in all. The constancy in their number is one of the characteristics that distinguish C. Xaymacana from the very closely related C. marsupialis of the Mediterranean. (Compare Fig. 3 with the similar one by Claus for C. marsupialis, ’78, Taf. I., Fig. 6.) The forked shape, while to be sure the common form in C. marsupialis, is an almost invariable characteristic in C. Xaymacana. It may be mentioned again that the presence of these canals is one of the chief features that distinguish the velarium of the Scyphomedusæ from the velum of the Hydromedusæ.
(c) _Canals of the Sensory Clubs and Tentacles._ The four interradial definitive tentacles and the four perradial transformed tentacles, the sensory clubs, are hollow, and their canals communicate directly with the peripheral part of the gastro-vascular system. The canal of the sensory club in each quadrant leads directly out from the stomach by a somewhat funnel-shaped opening formed by the approximation of the two walls of the stomach pocket. The relation of the canal of the sensory club to the stomach pocket is seen at a glance in Fig. 37. It is given by means of cross-sections in Figs. 12-14. Figure 12 shows the inner walls of the stomach pocket approaching the outer at two points, leaving between them a concavity freely open to the rest of the stomach pocket above and at the sides. Fig. 13, a little lower down, shows the two walls fused together at two points, making the interspaces a definite canal communicating with the stomach pocket above only. This canal lies directly over the sensory niche, and in the next figure (No. 14) the canal is seen to have passed through the roof of the sensory niche and to have entered the base of the stalk of the sensory club. In the enlarged end of the club, the part which bears the sensory structure, the canal widens into a terminal ampulla-like sac.