38 THE VOYAGE OF H.M.S. CHALLENGEE. 



begins to give off branches near its base, which attain to nearly the thickness of the 

 main stem. In one case the lowest branches anastomose with one another, the lowest 

 fuses again with the stem, so that it is difficult to recognise the regular ramification. 



Usually there arise four more or less thick branches from each calcareous joint of 

 the stem at difierent heights and on different sides. Still the tendency to develop the 

 branches, more particularly in one special plane, generally prevails. The largest 

 branches arise from two opposite sides and spread themselves out in the same plane, 

 while the other branches remain shorter. The branches arise at acute angles to the 

 stem. Each branch develops lateral twigs in the same manner as does the main stem, 

 and the ramification proceeds to the formation of twigs of the fifth order. Most of the 

 branches reach the summit of the main stem. 



The height of the colony reaches 120 mm. Diameter of the stem at the base 2 mm. 



Length of the main branches up to 45 mm., of the thin terminal twigs up to 10 mm. 



The polyps are small, inclined inwards towards the branches. They arise from 

 the branches and twigs at considerable intervals from one another, 0'8 to 1 mm. On 

 the larger twigs and branches mostly on three sides, on the terminal twigs only on 

 one side. 



Their form is club-shaped, the base broad, the mouth rounded ofi", the middle 

 constricted. Length, 0'8 mm. They seem, like the Primnoids, in a j^osition to bend 

 themselves inwards towards the branches. 



The calcareous joints of the axis are long, cylindrical, frequently bent and twisted. 

 In the main stem and larger branches 10 mm. long. The horny joints, on the other 

 hand, are very short, yellow-brown. The branches always arise entirely from the 

 calcareous joints and begin with a calcareous portion. The end twigs are calcareous, 

 often for a length of 18 mm.; they give off twigs and lateral twigs in which the horny 

 joints are completely absent, and thereby the tender terminal twigs of the colony acquire 

 a very fragile and brittle consistency. 



The spicules of the coenenchyma form three-sided and irregular longish scales, with 

 sharply toothed and incised edges, covered with numerous sharp spines. There are also 

 s^jindles with pointed warts. They hold firmly together by means of the toothed edges. 

 Their length to breadth in mm. reaches 0'15-0'03 ; 0'l-0"06. 



In the polyps the spicules form eight regular vertical rows of broad, flat, strong 

 scales, convex in accordance with the periphery of the polyp, strongly toothed and 

 covered with pointed warts. Their height to breadth in mm. reacbes 0'05-0"2 ; 

 0'05-0'15 ; 0"03-0"12. The scales lie upon a support of bent, thorny spindles of 

 0"08 mm. length, which form eight longitudinal rows. The tentacle sca,les .are broad, 

 uusymmetrical, in three rows. 



Habitat. — Station 320, ofi" the Eio de la Plata; depth, 600 fathoms; .bottom, green 

 sand. -i^i T- J jSi :.. .i 



