REPORT ON THE ALCYONARIxV. 43 



2. Mopsea encrinula (Lamarck) (PI. VII. figs. 1, la, lb; PI. IX. fig. 11). 



Isis encrinula, Lamk., Hist, auini. sans vert., t. ii. p. 302. 



Mopsea verticillata, Lamouroux, Hist. Polyp, flexibles, p. 467, pi. xviii. fig. 2, et Expos. m6th., 



p. 30. 

 Mopsea encrinula, Ehrenberg, Corallentb. d. rothen Meeres, p. 131. 



The colony is upright, ramified, the branches expanded in one plane. The main stem 

 gives off from two sides, alternating, plume-like twigs, which remain simple, on a few 

 larger branches which again bear plume-like twigs on two sides ; since the larger lateral 

 branches of the stem attain to the thickness and nearly to the length of the main stem, 

 and as the finer plumes come off at angles of 35° to 40°, the whole colony acquires a fan- 

 like appearance. 



Lensrth of the main stem 200 mm. Thickness at the base 2 mm. Length of one of 

 the two main branches 145 mm. Length of the feather-like branches 20 to 25 mm. 



The coenenchyma is thick, not transparent. The polyps are closely crowded on the 

 stem and twigs. On the stem and larger branches they are more developed on the sides 

 where the branches arise and leave the intervening coenenchyma free ; on the twigs, on 

 the contrary, they are arranged in close spirals. Each spiral is formed of five polyps, 

 but the spirals follow so close upon one another that each, on superficial examination, 

 looks like a whorl. The polyps are club-shaped, 1 mm. long. Their form very strongly 

 recalls that of the polyps of the Primnoids, with which they agree in being able to bend 

 themselves in towards the stem, as is always the case in death. The closed tentacles 

 form over the calyx an obtuse cone which recalls the closed operculum of the Primnoids. 

 The axis consists of horny and calcareous joints, which latter exhibit distinct longitudinal 

 furrows. In the lower part of the axis the horny joints are larger than the calcareous 

 joints. In one example the axis is horny up to 8 mm. above the base, further towards 

 the point the calcareous and horny joints become of equal length, and soon the calcareous 

 joints exceed the horny ones in length by more than double. 



The branches and plumes arise on both sides of the stem alternately, for from every 

 joint a twig comes ofl", on the one joint always from one side and on the next from 

 the opposite side. The first joint of the branch or twig is horny and arises from the 

 calcareous joint of the stem, but frequently close to the upper edge, so that its horny 

 base fuses with the horny joint of the stem or branch. This occurrence is very frequent, 

 and gave rise to the diagnoses of Ehrenberg and Milne-Edwards, that the branches and 

 twigs arise from the horny joints. 



In one .specimen, in the collection of the Jardin des Plantes, Paris, the origin of several 

 branches from the calcareous joints is easy to be seen. 



The spicules of this species are rough and thorny, those of the coenenchyroa are longish 

 lancet-shaped plates with sharp interlocking teeth on the edge. Length to breadth in 

 mm.— 0-1-0-05 ; 014-0-OG ; 0-13-0-05 ; 0-12-0-05 ; 0-1-0-03. 



