Genus: Charybdea.
Charybdeidæ with four simple interradial tentacles with pedalia; with velarium suspended, with velar canals and four perradial frenula. Stomach flat and low, without broad suspensoria. Four horizontal groups of gastric filaments, simple or double, tuft or brush-shaped, limited to the interradial corners of the stomach.
Species: Charybdea Xaymacana ([Fig. 1]).
Bell a four-sided pyramid with the corners more rounded than angular, yet not so rounded as to make the umbrella bell-shaped. The sides of the pyramid parallel in the lower two-thirds of the bell, in the upper third curving inward to form the truncation; near the top a slight horizontal constriction. Stomach flat and shallow. Proboscis with four oral lobes, hanging down in bell cavity a distance of between one-third and one-half the height of bell; very sensitive and contractile, so that it can be inverted into the stomach. The four phacelli epaulette-shaped, springing from a single stalk. Distance of the sensory clubs from the bell margin one-seventh or one-eighth the height of bell. Velarium in breadth about one-seventh the diameter of the bell at its margin. Four velar canals in each quadrant; each canal forked at the ends, at times with more than two branches. Pedalia flat, scalpel-shaped, between one-third and one-half as long as the height of bell. The four tentacles, when extended, at least eight times longer than the bell. Sexes separate. Height of bell, 18-23 mm.; breadth, about 15 mm. (individuals with mature reproductive elements); without pigment. Found at Port Henderson, Kingston Harbor, Jamaica.
As may be seen from the above, C. Xaymacana differs only a little from the C. marsupialis of the Mediterranean. Claus mentions in the latter a more or less well defined asymmetry of the bell, which he connects with a supposed occasional attachment by the proboscis to algæ. In C. Xaymacana I never noticed but that the bell was perfectly symmetrical. C. Xaymacana is about two-thirds the size given by Claus for his examples of C. marsupialis, which were not then sexually mature. It has 16 velar canals instead of 24 (32), as given by Haeckel, or 24 as figured by Claus. Difference in size and in number of velar canals are essentially the characteristics upon which Haeckel founded his Challenger species, C. Murrayana.
Family II: Chirodropidæ (Haeckel, 1877).
Cubomedusæ with four interradial groups of tentacles; with sixteen marginal pockets in the marginal lobes of the velarium, and with eight pocket arms, belonging to the exumbrella, in the four stomach pockets.
This family is represented in American waters by a species of Chiropsalmus, identified by H. V. Wilson as C. quadrumanus, found at Beaufort, North Carolina.