It will be seen from the above that Tripedalia possesses two of the characteristics of the Charybdeidæ and two of the Chirodropidæ. The family was named from the prominent feature of the arrangement of the tentacles, in groups of three with separate pedalia. The small size of T. cystophora is worthy of note in connection with the fact that of the twenty species of Cubomedusæ given by Haeckel in his “System” only two are smaller than 20 mm. in height, and those are the two representatives of Haeckel’s genus Procharagma, the prototype form of the Cubomedusæ, without pedalia and without velarium. While Tripedalia has both pedalia and velarium, it may be perhaps that its small size, taken in connection with characteristics just about midway between the Charybdeidæ and the Chirodropidæ, indicate that it is not a recently acquired form of the Cubomedusæ.
PART II: GENERAL DESCRIPTION OF THE ANATOMY OF THE CUBOMEDUSÆ.
1. The Cubomedusæ are generally believed to be inhabitants of deep water which come to the surface only occasionally. Both of the Jamaica species, however, were found at the surface of shallow water near the shore, and only under these circumstances. Whether these were their natural conditions, or whether the two forms were driven by some chance from the deep ocean into the Harbor and there found their surroundings secondarily congenial, so to speak, can be a matter of conjecture only. C. Xaymacana was taken regularly a few yards off-shore from a strip of sandy beach not ten minutes row from the laboratory at Port Henderson. It was seen only in the morning before the sea-breeze came in to roughen the water and to turn the region of its placid feeding-ground into a dangerous lee-shore. Some of the specimens taken contained in the stomach small fish so disproportionately large in comparison with the stomach that they lay coiled up, head overlapping tail. The name Charybdea, then, from the Greek χαρύβδις (a gulf, rapacious), seems to be no misnomer. It is worth mentioning that the digestive juices left the nervous system of the fish intact, so that from the stomach of a Charybdea could be obtained beautiful dissections, or rather macerations, of the brain, cord, and lateral nerves of a small fish.