REPORT ON THE DEEP-SEA MEDUSvE. 63 



Periphylla* Steenstrup, 1837. 



Periphyllidas with four perradial buccal pouches of the oesophagus and four perradial 

 completely separated niches of the basal stomach. Between these niches, the four 

 subumbral funnel cavities (or the four hollow interradial tasniola of the basal stomach) 

 form hollow cones, which are beset along their whole length by two rows of gastral 

 filaments and touch each other above in the point of the cone. 



The genus Periphylla, as well as the following closely allied genus Periphema, was 

 only presented in the Challenger collection by a single specimen. However, its large 

 size and its excellent state of preservation enabled me to examine it more minutely and 

 thoroughly than I had ever been able to examine any other Peromedusa. So that the 

 following description of Periphylla mirabilis with the six plates (XVIII.-XXIII.) may 

 be accepted as a firm foundation for the anatomical knowledge of the whole order of 

 Peromedusse. This conspicuous and remarkable group of Acraspeda was, till lately, 

 almost unknown. On the one hand, it keeps in many ways the primitive formation of the 

 Stauromedusse, and is more closely connected both with the Tesseridae and the Lucer- 

 naridse than the two orders of Cubomedusse and Discomedusse, especially with regard to 

 the remarkable formation of the central gastrovascular system. On the other hand, it 

 is raised so far above the other three orders of Acraspedae by the peculiar complication 

 of its anatomical structure, and specially by complicated formation of the pouches, that 

 in many respects it may be called the most highly developed of all Medusae. At any 

 rate, we must consider them as an independent principal group, as a special " order " of 

 Acraspedse, which have no direct connection with the Cubomedusae and Discomedusae, 

 but must be rather regarded as a peculiarly developed branch of the Stauromedusse. All 

 that was known of the wonderful Peromedusa? up to the year 1879 was limited to the 

 imperfect description of three different species of the genus Periphylla. But two of 

 these figures showed only the empty umbrella of the dead animal without any internal 

 organs — Charybdea periphylla, Peron and Lesueur (1809) ; and Charybdea bicolor, 

 Quoy and Gaimard (1833). The description of the third species, Dodecabostrycha 

 dubia, Brandt (1838), is partly good, partly very erroneous and incomplete, and 

 remained to be completely unintelligible. Detailed examination of several well- 

 preserved specimens of the stately Periphylla hyacinthina and some other smaller 

 species made by me on the genera Pericolpa, Pericrypta, and Peripalma first enabled 

 me, in 1879, to describe more minutely the hitherto unknown organisation of the Pero- 

 medusse, and to place them as an independent order of the class (in the System 

 der Medusen, pp. 396-422, Pis. XXIII., XXIV.). The anatomical description given 

 there will, however, be enlarged and completed in many points by the following more 



1 ritp;^i)xA«=set round with leaves. 



