EEPORT ON THE DEEP-SEA MEDUSAE. 31 



PolycoJpa, 1 Hseckel, 1879. 



Peganthidse with a simple reproductive girdle forming a broad ring in the lower wall 

 of the stomach (with genital cseca in the lobe cavities). Numerous (10 to 30) collar 

 lobes, and the same number of tentacles alternating with them. 



PolycoJpa is the simplest, and phylogcnetically the oldest genus in the family Pegan- 

 thidse, that peculiar group of Narcomedusse which are distinguished by the complete 

 want of the radial canals, and by the formation of a bow-shaped festoon canal. "Whilst 

 the most closely related Cunanthicke have still several true radial canals (in the form of 

 broad pernemal "gastral pouches "), these disappear completely in the Peganthidse, inas- 

 much as the strong tentacles by their dorsal change of position occupy the whole of 

 the umbrella margin up to the periphery of the stomach, where they are inserted. The 

 original radial canal (the " gastral pouch ") as well as the peronial double canal, undergo 

 retrograde formation ; both become lost. The annular canal, however, is divided into 

 the same number of isolated vessels as there are lobes of the umbrella collar. Each 

 horseshoe-shaped lobe canal or bow canal edges the margin of its lobe, and opens at 

 base of the latter immediately into the gastral cavity (beside the insertion of the 

 tentacles) by two separate mouths. The whole gastrovascular system in the Peganthidse 

 therefore consists only of the flat lens-shaped gastral sac and the circle of isolated lobe 

 canals, each opening with two mouths into the periphery of the stomach. Of the four 

 genera of the Peganthidse, which are all closely related, Polycolpa appears to be the 

 simplest and oldest form, as it has the primitive formation of the genitalia. The simple 

 genital girdle forms a broad undivided ring in the lower or subumbral wall of the 

 stomach. It does not send out csecal or pouch-like processes into the separate lobe 

 cavities as in the closely related genus Polyxenia and in the genera Pegasia and 

 Pegantha, derived from the latter. 



Polycolpa forskalii, Haackel (PI. X.). 



Polycolpa forskalii, Hfeckel, 1879, System der Medusen, p. 328, No. 350. 



Umbrella flat and discoid ; two to three times as broad as high. Twenty-five lobes, 

 nearly pentagonal ; none as long as broad. Genital girdle very broad, occupying nearly 

 the whole lower wall of the stomach. Twenty-five tentacles, three times as long as the 

 radius of the umbrella ; 130 to 170 auditory clubs (5 to 7 on each lobe). Horizontal 

 diameter, 20 to 30 mm. ; vertical diameter, 8 to 10 mm. 



Habitat. — The Indian and Pacific Oceans. I myself observed a living (female) 

 specimen of this species in the Ped Sea. It was taken in the tow-net at a depth of 

 above 60 fathoms, and the figures in Plate X. are drawn from it. I recognised, as I 



1 rio?ii/>!o>i7r«, with many curves (at the umbrella margin). 



