F. S. CONANT ON THE CUBOMEDUS^E. 17 



Hum of the depression. The reference numbers 1, 2, 3 and 4 denote the 

 same points in Figs. 32 and 33. Fig. 32 referred to Fig. 33 would lie in a 

 plane at right angles to the paper through the reference arrow x-v of the 

 latter figure. 



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 arid 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 Chary bdea two 

 marginal pockets ; or in all eight, a characteristic of the family Charyb- 

 deidse. 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 Glaus 

 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 character- 

 istic 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 Scyphomedusae from the velum of the Hydromedusse. 



(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 sen- 

 sory 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 

 3 



