HYDROMEDUSAE. 727 



Haeckel's classification of the family Cannotidae is primarily based upon the branching 

 of the radial canal system, and secondarily upon the number of main radial canals from the 

 stomach and the position of the gonads. The genera of this family have become somewhat 

 complicated, as both Anthomedusae and Leptomedusae have been mingled together. Haeckel 

 placed Wiliia oniata, McCrady (non Agassiz) in a new genus — Willetta, belonging to the 

 sub-family Williadae. Wiliia ovnata, A. Agassiz (non McCrady) is given a new generic and 

 a new specific name, Dyscannota dysdipleura, and placed in the sub-family Berenicidae. Haeckel 

 did not recognise the fact that Agassiz was describing the early and intermediate stages, showino- 

 the development of the canal system. 



Distribution. North Atlantic : United States ; South Carolina (McCrady). Massachusetts 

 (A. Agassiz). Rhode Island (Fewkes), (Brooks). 



Prohoscidactyla gemmifera (Fewkes), 1882. 



Wiliia ornata. Brooks (non McCrady), (1880); Brooks (1882). Wiliia gemmifera, Fewkes 

 (1882, p. 300, PL I.). Dyscannota gemmifera, Mayer (1900, p. 47, PI. VIII.). 



When Brooks first found this species with medusa-buds he considered it to be a stage 

 in the life-history of Wiliia ornata, McCrady. Fewkes succeeded in finding the first stage of 

 Wiliia ornata, McCrady, and reared it up to the adult without seeing medusa-buds, and, as 

 Agassiz had also described the early and intermediate stages without medusa-buds, Fewkes 

 considered Brooks's medusa-budding Wiliia to be a distinct species and jjrojjosed for it a 

 new specific name. Mayer fortunately found some specimens and has described them with 

 excellent figures. He has adopted Haeckel's system of classification, hence the generic name 

 Dyscannota. Mayer's figure shows that the medusa-bud, still attached to its parent, but ready 

 for liberation, has four radial canals, without branches, and four tentacles. The parent medusa 

 has two branches to each main canal, and twelve tentacles. Brooks's specimen belonged to an 

 earlier stage, having only one branch to each canal, and eight tentacles. 



The medusa-buds are upon stolons which hang down inside the cavity of the umbrella. 

 The stolons are situated on the radial canals at their juncture with the stomach, one stolon 

 on each of the four canals, and have at their free ends medusa-buds. 



Distribution. North Atlantic : United States ; North Carolina (Brooks). Tropical 

 Atlantic : oti' Florida ; in the Gulf Stream (Mayer). 



Prohoscidactyla tropica, species nova. 



Willsia sp. Huxley (1877, p. 120, fig. 17). 



This medusa has, up to the present, escaped having a specific name, and although figured 

 and partly described in the well-known textbook, " A Manual of the Anatomy of Invertebrate 

 Animals, " it was omitted by Haeckel in his Monograph. Huxley's description is as follows : 



" In August 1849, while in the North Pacific, off the Louisiade Archipelago, I took a 

 species of Willsia, in which stolons were developed at the bifurcations of each of the four 

 princijial radiating canals of the nectocalyx. Each stolon was terminated by a knobbed extremity 

 containing many nematocysts and gave rise, on one side, to a series of buds, of which those 

 nearest the free end of the stolon had acquired the form of a complete medusoid. They 



