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



the numerous tentacles being divided into sixteen isolated subradial bunches, so that 

 each bunch lies in the middle between a radial canal and an intercanalar adradial rib of 

 the exumbrella. A free auditory club is placed in the centre of each bunch upon a 

 projection on the lower side of the umbrella margin. The margin of the umbrella 

 appears distinctly divided by sixteen incisions (four perradial, four interradial, and 

 four adradial), into sixteen projecting lobes, each bearing a bunch of tentacles with 

 an auditory club. The eight mesogonia by which the umbrella cavity is divided into 

 eight funnels are strongly developed, as in Pectyllis, and the numerous caecal centripetal 

 canals between the radial canals, by which Pedis is distinguished, are also wanting as 

 in Pectyllis. 



Pectanthis asteroides, Hseckel (Pis. VII., VIII.). 



Pectanthis asteroides, Hseckel, System der Medusen, p. 267, No. 289. 



Umbrella depressed to a hemisphere ; two to four times as broad as high. Ex- 

 umbrella with sixteen radial ribs. Stomach quadra ngularly prismatic ; nearly as long as 

 the radius of the umbrella. Mouth four-lobed, extensible into an octagonal sucking- disk. 

 Eight egg-shaped genitalia in the proximal half of the radial canal, encircling the basis 

 of the stomach in the form of an eight-rayed star, and halved by long radial mesogonia. 

 Umbrella margin swollen, thickened, with sixteen intercostal protuberances or marginal 

 lobes, each bearing a subradial auditory club and a pencil-shaped tuft of twelve to sixteen 

 tentacles. Tentacles hollow, of unequal length, the longest equal to the radius of the 

 umbrella, generally with a sucking-disk at the end. Horizontal diameter, 5 mm. ; ver- 

 tical diameter, 2 mm. 



Habitat. — The Mediterranean. I myself caught a living specimen of this deep-sea 

 Trachomedusa with the tow-net in the Adriatic Sea on April 15, 1878, at a depth of 

 200 fathoms, some miles distant from Pola. The following description and the figures 

 on Plates VII. and VIII. are prepared from this specimen (a mature male), which was 

 examined alive. I also found a small specimen of the same species, which did not 

 admit of any minute investigation, but still furnished proof of its identity in a bot- 

 tom specimen from the Challenger collection from Station 4, at the entrance of the 

 Straits of Gibraltar. Lat. 36° 25' N., long. 8° 12' W. 16th January 1873. Depth, 600 

 fathoms. 



In the example which I observed alive in Pola, the umbrella in a contracted condition 

 had an almost hemispherical bell shape. In a dilated condition, on the other hand, it 

 appeared distinctly depressed, so that the largest horizontal diameter was three to four 

 times greater than the largest vertical diameter. The former measured 4-5 mm., the 

 latter 1-2 mm. 



The exumbrella or the external convex surface of the umbrella is divided by sixteen 



