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



consists of eight fairly equally developed triangular scales. The spicules of the coenen- 

 chyma form two layers. The u]^per layer consists of flat, thin, oval scales, the lower of 

 very thin, small, calcareous plates. 



[Plumarella penna (Lamarck). 



Gorgonia penna, Lamk., Hist, aniin. sans vert., ii. p. 32.3. 



Primnoa (?) plumaHlis, Milne-Edwards, Hist. Nat. des Coralliaires, t. i. p. 141. 



„ „ Kent, Monthly Micr. Journ., 1870, pi. xli. figs. 10-12 (figure of spicules). 



Cricogorgia ramea, Milne-Edwards, loc. cif., Atlas, pi. B.2. fig. 6. 



Habitat. — Australia, Captain Baudin's Expedition, 1801. 



Plumarella pourtalesi, Verrill. 



Habitat— Lsit. 31° 48' 50" N., long. 77° 51' 50" W. (VerrHl).] 



1. Plumarella delicatissima, n. .?p. (PI. XVI. figs. 1, la; PI. XXI. fig. 8). 



Some fragments of a Plumarella show such specific differences from any known form 

 that they necessitate the foundation for them of a new species, which may be described 

 as follows : — 



Colony exceedingly finely branched, the terminal twigs very thin, flexible. The 

 small, cylindrical calyces are placed on two sides of the branches and twigs in alternating 

 series, their length reaches 0'5 to 0"7 mm. The calyx scales form five longitudinal rows 

 of thin, cycloid, calcareous bodies, which are wanting on the ventral side of the calyx. 



The opercular scales form a blunt cone, which does not completely close the calyx 

 opening. 



The main stem, of which the base is wanting, is flattened in one plane ; at its lower 

 end the larger diameter reaches 2*5 mm. Its axis is hard, horny, calcareous, on the 

 surface shining, with numerous longitudinal furrows. From two sides arise from it, in 

 alternating series, small thin twigs, of barely 0'5 mm. diameter, and larger branches 

 which have at the beginning a diameter of 2 mm. All these come off from the stem at 

 an angle of about 40° and run parallel to one another. 



At the point of origin of each twig the stem undergoes a slight twist in the opposite 

 direction, whereby the stem acquires a zigzag outline. The small branches either 

 remain simple or give off at most two or three lateral tw^igs, the large branches, on the 

 contrary, ramify after the manner of the main stem ; the same is the case with the 

 larger secondary twigs of the latter, and so on, so as at length to give rise to a little 

 shrub exceedingly finely ramified in one plane, the simple terminal twigs of which have a 

 diameter of 0"3 mm. and a length of 15 to 30 mm. 



