MUSEUM OF COMPARATIVE ZOOLOGY. 307 



mentioned above. In them individual eggs can be easily distinguished in the 

 chromic acid specimen. The diameter of the larger specimen Is ahout three 

 fourths of an inch. 



The combination of structures which could be made out with any certainty 

 in these two specimens of Halicreas certainly stamp it as a most pecubar jelly- 

 fish. Little stress, however, can be placed on the failure to find certain essen- 

 tial organs, as the tentacles, otocysts, and the like. Tentacles may have existed 

 and have been broken off in the capture of the medusa, leaving the bases as 

 stumps. Such a condition almost invariably results in alcoholic Trachyme- 

 dusse. If I am not wrong in my interpretation of the systematic position of 

 Halicreas, the otocysts, if any exist, should be searched for on the inner or 

 lower rim of that body which has been called the velum. In both the speci- 

 mens before me that structure is so contorted that, even if sense organs existed, 

 they could not be found or counted. There are certainly no marginal sense 

 bodies on the interval between each marginal tubercle. 



The knowledge which we have of the structure of this medusa is so frag- 

 mentary that it is at present impossible to determine its affinities. It seems to 

 me most closely allied to the Narcomedusse, Haeckel, but differs from them all 

 in the eight radial stripes in the bell and the eight marginal tubercles. On 

 the other hand, there are no marginal lappets as in Discophora, and the 

 "velum " indicates a true hydroid medusa. The prominent marginal tubercles 

 at their extremities are wanting in all other medusa; with which I am ac- 

 quainted. The genus is the type of a new family related to the Discophora 

 more intimately than are the Narcomedusae, among which it will probably be 

 placed. 



