396 bulletin: museum of comparative zoology. 



(Bigelow, 1909a, p. S3). It, like P. triloba, has comparatively few 

 tentacles (9-13) and a high-arched bell; but it is separated from that 

 species by the limitation of the exumbrella-sculpture to the marginal 

 lappets, and especially by the structure of the gonads, which are simple 

 in the young, and though more or less lobed and irregular in the adult 

 (Bigelow, 1904, pi. 18, fig. 6), never definitely subdivided, or trifid, 

 as they are in P. triloba. The Medusa from the Maldive Islands which 

 I described (1902) as P. simplex, is P. martagoji. Pegantha zonaria 

 Haeckel is apparently close to, if not identical with it, as may also be 

 the Pegasia dodecagona of Peron and Lesueur (1809), redescribed by 

 Haeckel (1879). And this is likewise true of the Medusa mollicina 

 Forskal (1775), redescribed by Haeckel (1879), as Polyxenia viollicina. 

 But these early descriptions are so unsatisfactory that it is doubtful 

 whether they can ever be definitely connected with any actual Medusa. 



All other Peganthas recorded within recent years have sixteen or 

 more tentacles, in connection with a low flat bell, with the exumbrella 

 sculpture much less prominent than that of P. triloba. Such are P. 

 daciyletra Maas (1893), P. clara R. P. Bigelow (1909), P. smaragdina 

 H. B. Bigelow (1909a), and the Peganthas described by Vanhoffen 

 (1908a, 1912a, 1912b), as " Polycolpa forskalii" Haeckel, and " Poly- 

 xenia cyanostylis" Eschscholtz. 



Pegantha laevis, P. daciyletra, and Vanhoffen's "P. cyanostylis" 

 agree so closely with one another in the structure of the gonads, which 

 consist of swellings with papilliform lobes or processes, and in the 

 number of tentacles, that, they may prove to be identical. But so 

 unsatisfactory are the accounts of P. cyanostylis by Eschscholtz (1829) 

 and by Haeckel (1879) that its identity with any actual Medusa must 

 always remain in doubt. 



In P. smaragdina and P. clara the gonads are simple; and they 

 agree with one another closely in tentacle-number, (21-34), and general 

 form; the only differences between them are the degree of convexity 

 of the subumbral side of the disc, and color, P. clara being colorless, 

 whereas in P. smaragdina^ the stomach and canal-system are lemon- 

 yellow. And since neither of these characteristics is apt to be of much 

 significance, judging from other Medusae, Vanhoffen (191^^) is proba- 

 bly correct in uniting them, though final decision must await larger 

 series of each than have yet been studied. The specimens described 

 by Vanhoffen (1908a, 1912b) as Polycol pa forskalii Haeckel, may per- 

 haps belong here too, though since the gonads were not present, 



' The descriptions of P. smaragdina H. B. BiKelow (1909a) and of P. clara R. P. Bigelow 

 (1909) appeared almost simultaneously. 



