36 



MEDUSA. I. 



Ptychogena antarctica Browne (1907, more thoroughly described in 1910, p. 29) is distinguished 

 from Ptychogena lactea by the fact that the gonadial lateral folds are shorter and not attached to the 

 subunibrella, and by the colour, the base of the tentacles being, according to Browne, provided with 

 red entodermal pigment; according to Vanhoffen (1912), who has refound the species in the material 

 from the German South-Polar expedition, the organs are dark coffee-brown. There is one cordylus be- 

 tween every successive pair of tentacles, and in some of these cordyli Browne found nematocysts (see p. 4). 



Chart III. Occurrence of Ptychogena lactea A. Agassiz in the northern Atlantic and adjacent arctic waters. — The hatching 

 denotes the southern limit of the occurrence in the Barei^ts Sea, according to Linko. 



Vanhoffen (1912, p. 366) describes another species, Ptychogena aurea, from four small speci- 

 mens with about 32 tentacles and gold-yellow gonads with mature sexual products. Cordyli are not 

 present. I am not convinced that this medusa belongs to the genus Ptychogena^ but I will not deny 

 the possibility. 



I have had at my disposal for examination 12 specimens of Ptychogena lactea from 9 different 

 localities. In the following list I have also included some non-preserved specimens from Godthaab 

 Fjord, Greenland, found by the "Tjalfe" expedition; in the journal of the expedition they are shortly 

 but clearly described, so much so that they may be identified with complete security. 



