44 EDWAED T. BKOWNE. 



Dr. Mayer (1906) has described and figured some specimens of P. dodecabostrycha 

 taken by the 'Albatross' oft" the Hawaiian Islands in June, 1902, at the depth of 

 577-480 fms. and 478-453 fms. The smallest specimen was 55 mm. high and 

 50 mm. wide at the tentacular zone, and the largest 70 mm. high and 100 mm. wide. 

 From the description and figures these specimens agree very well with those in the 

 Antarctic collections. Mayer draws attention to the shape of the umbrella changing 

 with age, becoming flatter and relatively wider as the Medusa grows larger. All the 

 specimens taken by the 'Albatross' were deeply pigmented with brownish purple, 

 especially in the zones of the radial and circular muscles. Mayer is of the opinion 

 that it is possible that all of the so-called species of Peripliylla may in the end prove 

 to be local races of one and the same form. 



After the first examination of the specimens in the Antarctic collections I felt 

 fairly sure that they were large specimens of Peripliylla hyacinthina. My determination 

 was based not so much upon the shape of the umbrella, or upon the amount of 

 pigmentation, as upon the shape of the pedalia. All the specimens have the rhopaliar 

 pedalia longer and narrower than the tentacular ones. In this respect they resemble 

 Haeckel's figures of P. hyacinthina. 



The rounded shape of the top of the umbrella is in favour of the specimens being 

 Periphylla regina. But after comparing Dr. Wilson's sketch (Plate VII., fig. l) with 

 Agassiz's sketch of P. regina, drawn and coloured from life (see Maas, 1897, Taf. X.), 

 I came to the conclusion that the specimens did not belong to that species. According 

 to Prof. Agassiz's figure the pedalia of P. regina are semi-globular in shape, and all of 

 the same size. 



At present the three species of Peripliylla are mainly distinguished by the 

 shape of the umbrella and by the colour and amount of pigmentation. I think 

 that we require a better and more definite character for the determination 

 of the species, especially as the identification has usually to be based upon preserved 



specimens. 



If Periphylla hyacinthina and P. dodecabostrycha be really distinct species, then 



I think a character could be found upon the margin of the umbrella, such as the shape 



of the pedalia, by which they could be readily distinguished. 



I have placed the specimens collected by the ' Southern Cross ' and ' Discovery ' 



under the name of Periphylla dodecabostrycha because they agree very well with 



Haeckel's P. mirabilis, which is considered to be identical with P. dodecabostrycha. 



I am rather in favour of Mr. Bigelow's suggestion that the small P. dodecabostrycha, 



described by Messrs. Maas and Vanhoffen, are young stages of P. hyacinthina. 



I am also inclined to think that the large specimens called P. mirabilis and 



P. dodecabostrycha will eventually be proved to be only very large specimens of 



P. hyacinthina. 



