261 



Coenenchyma, 1") x 017") ; OS x 15 ; 00 x 01 ; 04 x 0075. 

 Anthocociiii?, 0-() x 0-075 ; 04 x 01 ; 04 x 005 ; 0-3 x 0-05. 

 The colour of the colony is a greyish white. 

 Locality : Andamans, 270-45 fathoms. 



Family Plexa urid.e. 



Plexaitra i7idica, Ridley. 



Plexauroides praelonga (Ridley) = (P^e.cau7'a praelonga, Ridley). 



Psammogorgia ridleyi, n. sp. 



GENUS PLEXAURA, Lamouroux. 

 Plexaura indica, Ridley. 



Belonging to this species is a very beautiful orange-yellow colony 150 mm. 

 high and 170 mm. broad. It is branched almost in one plane and consists of a 

 main stem 12'5 cm. high from which seven liranches arise at intervals of 2 ram. 

 to 6 mm. The main stem arises abruptly from a spreading base overgrown by 

 coinenchyma. The diameter near the base is 3 mm. and this scarcely diminishes 

 even in the branches, the tips of which are somewhat clavate. The branch- 

 ing is quite irregular, the larger branches giving rise to secondaries in the 

 same way, though there is a tendency in some parts to arise from one side. The 

 angle of origin also varies from 60° to 90°, and all the branches eventually diverge 

 upwards in a sinuous manner. 



The coenenchyma is moderately thick and very rough in appearance. With 

 a low power it is glistening and arenaceous, being uniformly covered with small, 

 smooth, globular projections. It consists of two layers, the outer composed of 

 somewhat club-shaped spicules disposed perpendicularly to the axis, the inner 

 consisting of spicules of very diverse form arranged irregularly. In several places, 

 especially between the polyps, there are marked ridges foi'med by segregations 

 of spicules. 



The polyps are scattered over the whole surface, the verructc being incon- 

 si)icuous. They are separated by distances of about 0'5 mm. and have elongated 

 mouth openings. The anthocodite are small, white and wholly retractile. 

 When partially withdrawn the infolded tentacles present an eight-rayed figure 

 which eventually disappears when the walls of the verruca? close together. 



The axis is horny and cylindrical. The colour varies from brown at the 

 base to a pale yellow in the twigs. It is composed of irregular longitudinal 

 strands which in the younger portions present a very pretty variegated appearance. 

 The core is soft and white and is divided into chambers by horizontal partitions. 



The spicules of the outer layer of the coenenchyma are distinct in having a 

 globular expansion which projects on the surface, but the part embedded in the 



