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



The polyps when extended consist of three portions, a basal portion armed with 

 spicules, the calyx ; an intermediate portion containing chiefly the oesophagus ; and a 

 tentacular portion which contains the oral disk and the eight pinnate tentacles. 



When the polyp is retracted, the oesophageal portion, which contains no spicules, 

 folds itself inwards, the tentacles bend together inwards over the oral disk, and the 

 tentacular portion eventually assumes a position covering over the body; the margin of 

 the oral disk sometimes completely withdraws itself, carrying in with it the basal portion 

 of the tentacles. 



The spicules of the ccenenchyma consist of spiny needles, sometimes with dentate 

 prominences, which are sometimes straight, sometimes curved, or even bent at an angle. 

 At the base of the calyx they are arranged in the form of a ring, and are furnished with 

 spiny prominences, some of which become expanded, thus gradually taking the form 

 called " Stachelplatten " by KoUiker. On the calyx itself they form converging series, 

 which are arranged in eight longitudinal rows en chevroii. The oesophageal portion has 

 no spicules ; they first appear under the base of the tentacles and form there a colleret 

 of horizontally placed spicules. The base of the tentacles contains spicules placed in a 

 longitudinal direction, but they only appear on the portion of the tentacle turned away 

 from the mouth. These are elongated, spine-like ; often a little bent, and mutually 

 converging from either side. When the polyp is retracted, the colleret lies exactly 

 around the upper edge of the calyx, and the spicules of the base of the tentacles form a 

 covering over the calyx-opening, while the unarmed oesophageal portion is completely 

 folded inwards. 



There are three species in the collection of the Challenger, from the Atlantic Ocean 

 and from the south-west coast of South America. 



1. Paramuricea wquatorialis, n. sp. (PI. XXII. fig. 6 ; PI. XXVI. fig. 3). 



The stem is branched in one plane, and is vertical. The branches are bent and curved 

 in various directions. The principal stem has a length of 140 mm., its thickness at the 

 base is about 3 mm., and it is somewhat compressed. The branches, of which some are 

 equal in thickness to the principal stem, arise forming with it an obtuse angle, and opposite 

 to each other. The larger ones develop lateral branches, which arise only on the side 

 turned away from the stem. Branches of a third order are rarely developed, and are 

 then but short. The stem and its ramifications form long unbranched tendril-hke twigs, 

 which are a little thickened at their terminal points ; these latter are from 30 to 35 mm. 

 long. The longest branch arising from the lower third of the stem has a length of 

 100 mm., and at its base it is 2 mm. in diameter ; it gives ofi" branches which also produce 

 side twigs. 



The polyps arise irregularly from the stem and branches in two or three rows but 



