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New Zealand Coelenterates Ctenophores from Cook Strait

Pleurobrachia helicoides sp. now Text Fig. I

Pleurobrachia helicoides sp. now Text Fig. I .

Specific Description: Body of living specimen cylindrical, with long comb rows extending from the aboral pole to nearly the oral pole; meridional canals slightly greater in length than the comb rows broad paragastric canals, nearly as wide as the stomodeum; tentilla. tightly coiled into a barrel-shaped helix, orange-pink in colour.

Text Fig. I.

Text Fig. I.

Pleurobrachia helicoides n.sp. P, paragastric canal; TB, tentacle base; TS, tentacle sheath; TT, coiled helix of tentilla; S, stomodeum.

Specimens were taken on two occasions—July 22nd and 23rd 1935. They were very active swimmers and intolerant to any irritation. The specimen described below page 3 was 11 mm. long, approximately cylindrical, with blunt oral and aboral ends. The eight bands of swimming plates almost cover the eight meridional canals and extend from the aboral pole to nearly the mouth rim. A faint pink colour can be distinguished underneath the comb rows. The two long contractile tentacles are based in the usual position for Pleurobrachia—midway between the outer body wall and the funnel axis. The tentacles give rise at long intervals to lateral filaments tightly coiled into barrel-shaped helicles which are orange-pink in colour. To the naked eye the tentacle resembles the fishing thread of a young Physophora. The helicles were not seen to uncoil. The bottom of the tentacle sheath is filled with liquid of refractive index similar to the oil bubble in a fish egg. The apical sense organ when first examined in the living animal is prominent, projecting above the polar surface, but as the specimens become fatigued it sinks into a pit and the surrounding tissue between the swimming plates swells upward to form the walls of the pit. The funnel tube is nearly one-third the length of the body, and of constant diameter. The paragastric canals are greatly flattened and very wide, as wide as the stomodeum. No genital products are visible in the meridional canals.