212 THE MEDUSAE. 



been described. The nearest ally appears to be the Atlantic species T. coeca, 

 of which Hartlaub ('92) has given an excellent account. 



Bythotiaridae Maas, 1905. 

 ' sens. em. 



In 1905 Maas described, from the collections of the-"Siboga" expedi- 

 tion, the new genus Sibogita, for a single specimen of a new species related, 

 in tentacle structure, to the Tiaridae, but, like Bythotiara Guenther (:03), 

 apparently having branched canals. In the present collection there are two 

 specimens which very closely resemble Sibogita in general form and struc- 

 ture of bell margin, gonads and manubrium, but which differ from the type 

 of that genus in the structure of the canals. These are not branched, but 

 in addition to the four radial canals there are eight blind adradial canals 

 extending from the margin centripetally almost to the apex of the bell. 

 Fortunately both specimens show this feature so clearly that it is easily 

 demonstrable by photography. Dr. Maas, on examination, pronounced these 

 specimens at least generically distinct from his Sibogita, and suggested that 

 they might be the adult of his provisional genus Heterotiara ; but the dis- 

 covery, in the present collection, of adult specimens of the latter genus 

 resembling his original account of Heterotiara in all characters, except 

 those of growth, renders that solution improbable. It seemed to me so 

 unlikely that the close general resemblance between the present specimens 

 and Sibogita could be connected with generic difference that I was in doubt 

 as to what disposition to make of them when I received from the United 

 States National Museum a specimen which threw an entirely new light on 

 the question. This specimen, which is more advanced than those collected 

 by the "Albatross," though less so than the single " Siboga " specimen, seems 

 to show that the appearance which led Maas to conclude that the canals 

 are branched is not the primary one; but is secondarily induced by a union 

 of the blind canals with the four arms of the cruciform base of the manu- 

 brium by further centripetal growth. If the canals of Sibogita are not 

 primarily branched, we must either remove it from the Bythotiaridae or 

 modify Maas's (: 05) diagnosis of that family. Of the two courses the latter 

 seems to me preferable, inasmuch as Sibogita so closely resembles both 

 Bythotiara Guenther and Heterotiara, in the permanently iriterradial loca- 

 tion of its gonads, the structure of the bell margin, the hollow tentacles, and 



