64 THE VOYAGE OF H.M.S. CHALLENGE!;. 



detailed anatomy of Periphylla mirabilis. This species, as well as the following species, 

 Pervphema regina belong to the family of the PeriphyUidse, these large and highly 

 organised Peromedusse which have twelve tentacles, sixteen marginal lobes, and thirty- 

 two lobe pouches. Contrasted with these stand the older and more simply constructed 

 Pericolpitis;, which are more closely connected with the Lucernaridas, and have only four 

 perradial tentacles, besides eight marginal lobes, and sixteen lobe pouches. Each perradial 

 tentacle of the Pericolpidse is represented in the PeriphyUidse by three tentacles, and two 

 marginal lobes inserted between them. All Perom'edusfe have invariably only four 

 interradial rhopalia, and this alone distinguishes them from all other Medusae. Our 

 Periphylla mirabilis is distinguished from all other species of the genus by the eight 

 strong barbous filaments of the margin of the mouth, and may therefore be regarded 

 as the representative of a distinct genus — Periphenga mirabilis (irepi^iyya, radiating). 



Periphylla mirabilis, Hseckel (Pis. XVIII.-XXIIL). 



Periphenga mirabilis, Hreckel, 1879, System der Medusen, p. 422, Xo. 424. 



Umbrella conical, about one-fourth higher than broad. Pedal zone of the exunibrella 

 somewhat higher than the lobe zone, both together nearly three-fourths as high as the 

 cone zone. Marginal lobes oval, pointed ; their distal wings triangular, half as high as 

 their proximal gelatinous swelling. The eight tentacle lobes projecting less than the 

 eight rhopalia lobes on the umbrella margin. Tentacles twice as long as the height 

 of the umbrella, one-third as broad as the marginal lobes at their basis. (Esophagus 

 cubical, one-third as high as the umbrella, reaching only to the coronal muscle, with 

 eight adradial, long, feathered, barbous filaments at the margin of the mouth. Hori- 

 zontal diameter, 120 mm. ; vertical diameter, 160 mm. 



Habitat. — South Pacific Ocean, near the east coast of New Zealand. Lat. 40° 28' S., 

 long. 177° 43' E. Station 168. The single specimen captured, a mature male, was 

 taken July 8, 1874, at a depth of 1100 fathoms. It was admirably preserved in spirit, was 

 quite perfect ; and was, on the whole, of a pale violet colour. The inner or endodermal 

 surface of the gelatinous umbrella was overlaid with dark, violet-brown pigment, which 

 was easily rubbed off, and consisted of small roundish granules in the endodermal cells of 

 the abaxial wall of the gastral space. The tentacles appeared coloured darker violet, the 

 genitalia reddish-yellow. After lying some years in spirit, the colours become fainter. 



The umbrella (PI. XVIII. fig. 1 ; PL XIX. fig. 6 ; PI. XX. fig. 8 ; PL XXI. figs. 

 12-20) of Periphylla mirabilis, as of most other Peromedusse, is high-arched, conical, 

 pointed above, and widened like a funnel below, or almost helmet-shaped. The height (or 

 vertical diameter) of the umbrella — including the marginal lobes, excluding the tentacles 

 — amounted in the uninjured specimen to 16 centimetres; therefore, one-fourth more 

 than the breadth at the opening of the umbrella, 12 centimetres being the largest 

 horizontal diameter. Almost in the middle of its height, — 8^ cm. from the umbrella 



