Medusas of the Philippines and of Torres Straits. 



173 



in the radius of each tentacle and rhopalium, 16 in all. These vessels fork 

 before reaching the tentacles or rhopalia, and their diverging ends curve around 

 the edges of the lappets and form a marginal ring-canal. 



I believe that Periphylla hyacinthina can not be separated specifically from 

 P. dodecabostrycha. The shape of the bell is quite variable, and when large 

 the medusa usually becomes relatively flat and dome-like, whereas it is rela- 

 tively high and conical when young. P. hyacinthina is said to be densely 

 pigmented with purple-brown so that the gonads can not be seen through the 

 bell walls, whereas P. dodecabostrycha is said to be less densely colored and 

 semi-translucent. This distinction does not always apply and certainly the 

 degree of pigmentation appears to be quite independent of the shape of the 

 bell, whether flat and dome-like or high and pointed. Browne (1910), in his 

 study of the Scyphomedusse of the Atlantic National Expedition, concludes 

 that P. dodecabostrycha is probably only a large-growth phase of P. hyacin- 

 thina, and with this opinion I am heartily in accord. 



Periphylla hyacinthina Steenstrup. 



The Albatross obtained 21 specimens of this common deep-sea medusa 

 among the Philippine Islands, between depths of 338 and 1,291 fathoms, as 

 follows : 



Genus LINUCHE Eschscholtz, 1829. 



Linuchf, ESCHSCHOLTZ, 1829, Syst. der Acalephen, p. 91. 



GENERIC CHARACTERS. 



Coronatse with 8 rhopalia, 4 perradial and 4 interradial. 8 tentacles, 16 

 marginal lappets. With hernia-like sacs of the gastrovascular cavity pro- 

 truding from the floor of the subumbrella. 8 gonads grouped in 4 pairs close 

 to the 4 perradii. The central stomach opens by 4 perradial ostia into a ring- 

 sinus which in turn breaks up into 16 branching, radiating pouches in the 

 lappets. A marginal ring-canal is present in the Pacific L. aquila, and accord- 

 ing to Vanhoffen also in L. unguiculata of the Atlantic. 



