86 THE VOYAGE OF H.M.S. CHALLENGER. 



the crescentic folds at the end of each longitudinal furrow. The umbrella corona may 

 be subdivided into an upper pedal girdle and a lower lobe girdle. The pedal girdle 

 ("zona pedalis") is, however, much less strongly developed than in most other Periphyllidse, 

 and hardly 2 cm. high. The pedalia are slightly vaulted and comparatively small. The 

 lobe girdle of the umbrella corona (figs. 1,2," zona lobaris ") is more strongly developed 

 in Periphylla regina and differently shaped from that of Periphylla mirabilis. The sixteen 

 subradial marginal lobes are much larger compared to the pedalia, and are rounded, not 

 pointed. The difference in size between the four pair of ocular lobes, and the four 

 pair of tentacle lobes alternating with them is considerably greater. Neither the two 

 gelatinous swellings lying in each marginal lobe nor the inter-furrow are so thick as in 

 Periphylla mirabilis; the lobe clasp (" loboporpa," fig. 2, kl), which lies at the bottom 

 of this furrow, and supports the septum between the two halves of the pouch, is much 

 feebler, but shows the same structure in transverse section, fig. 10, comp. above, p. 

 71), on the other hand, the thin delicate wings (" patagia," Ip), which form the selvage 

 of the lobe margin, are much broader and longer in our species than in the foregoing. 

 If we measure from the circular line of the exumbrella, indicated by the insertion of the 

 tentacles between the marginal lobes, the tentacle lobes are 50 mm. long (without wings, 

 35 mm.), and the ocular lobes only 45 mm. (without wings, 30 mm). The tentacle lobes 

 are more than 30 mm. broad in the middle, the ocular lobes a little over 20 mm. (figs. 

 1,2). 



The four interradial sense clubs in this species appear to be very small and almost 

 rudimentary (fig. 2, o) ; in the fragment, to hand, however, there was only one preserved, 

 and it did not allow of closer investigation. Only half of the twelve tentacles were 

 preserved (figs. 1, 4). They are on the whole of the same nature as in the preceding- 

 species (comp. above, p. 67), but are considerably shorter and thicker. Their length is 

 nearly equal to the height of the umbrella (18-20 cm.), whilst in Periphylla mirabilis it 

 is twice as great. The longitudinal muscle appears to be less strongly developed. The 

 thickness of the hollow tentacles at the conically swollen base amounts to 10 mm. They 

 then thin away into a cone and run out below into a fine point (fig. 2, t). The 

 peculiar insertion of the tentacle by two root muscles (mk) inside a tentacle funnel (it), and 

 the remarkable formation of the double-valved vent-hole at its base, is the same here as 

 has been already described in Periphylla mirabilis (comp. PI. XXII. fig. 22, and PI. 

 XXV. fig. 1). 



The inner concave umbrella wall (subumbrella, PI. XXIV. fig. 1 ) in Periphema regina 

 shows on the whole the same conditions already (p. 71) described in detail in Periphylla 

 in irabilis. The muscular system is, however, much more strongly developed in the former, 

 and the separate muscles show more prominently. The eight longitudinal deltoid muscles 

 ("musculi deltoidei") are yellowish-white, very stout, firm glistening bands, and appear re- 

 markably powerful. The strongest is the interradial deltoid muscle (fig. 1, md'), an equila- 



