400 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.40. 



medusan family, the only confusion being in the case of genera insuffi- 

 ciently studied. They all agree in the structure, though not in the 

 location, of the otocysts, and in the fact that the primary tentacles, 

 which of course arise from the bell margin, turn upward as they grow 

 older, lying in f un*ows of the exumbrella, so that they emerge from the 

 bell at some height above the margin. But these tentacles may or 

 may not bear suckers, or terminal knobs; there may or may not be 

 a second series of marginal tentacles, or the latter may be represented 

 by clubs; there may or may not be centripetal canals between the 

 radials; the otocyst capsules may be free; they may be embedded 

 in the exumbrella, or in the velum ; the tentacles may be in continuous 

 series or they may be grouped ; and there may be either 4 or 6 meta- 

 meres. The presence or absence of secondary tentacles and of centrip- 

 etal canals, of course, allow four possible combinations of which three 

 were previously known, while the new genus Eperetmus, here de- 

 scribed, exemplifies the fourth. 



The combinations of characters as found in the various genera may 

 be illustrated by the following tabular view (which is, of course, purely 

 artificial) : 



a ^ With primary tentacles only. With 4 metameres. 

 b '. Tentacles in a simple series, 

 c '. No centripetal canals. 



d '. Otocyst capsules free Aglauropsis. 



d 2. Otocyst capsules embedded in the velum Craspedacusta. 



c 2. With centripetal canals Eperetnuts, new genus. 



b ^. Tentacles in groups. 



No centripetal canals Gossea. 



a ^. With primary tentacles, and secondary marginal clubs. 

 With 4 metameres. 



b '. No centripetal canals. Tentacles with suckers Gonionemus. 



b 2. With centripetal canals. Tentacles without suckers (?) Maeotias. 



a '. With both primary and secondary tentacles, the former with suckers. 

 b ^ With 4 metameres. 

 c '. No centripetal canals. 



rf ^. 4 primary tentacles only Vallentinia. 



d 2. Many primary tentacles Cubaia. 



c 2. With centripetal canals Olindia$. 



h 2. With 6 metameres. 



With centripetal canals Olindioides. 



Six of these genera, Craspedacusta, Gossea, Gonionemus, Cubaia, 

 Olindias, and Olindioides, are well known anatomically. The remain- 

 ing three demand further research. One at least of them (Vallen- 

 tinia) may finally prove to be a young stage of some other. There is 

 no possibility, however, that this can be true of the new genus Eperet- 

 mus, for it is separated from most of its family relatives by positive, 

 not negative characters, the presence of centripetal canals distin- 

 guishing it from Aglauropsis, Craspedacusta, Gossea, Gonionemus, and 



