266 



GENUS NICELLA, Gray. 

 Nicella reticulata, n. sp. 



Plate IV. fig. 5; Plate VIII. fig. 12. 



Over a dozen specimens of pecnliar colouration represent this species. A 

 typical colony measures 27 cm. in height by 16 cm. in maximum breadth, and 

 is attached by a very much broadened expansion. It consists of a main stem 

 only 2 cm. long and measuring 4'5 mm. in diameter. At the distal end of the 

 main stem four branches arise, two sub-opposite and two at slightly difterent 

 levels, but all very close together. These diverge at varying angles, the two 

 lower being almost horizontal, the other two also in the same plane of ramifica- 

 tion. These I'amify irregularly in one plane and anastomose freely, forming a 

 large almost semicircular flabelliform mass with very irregular meshes. 



The coenenchyma is thin and compact, and presents a glistening arenaceous 

 appearance. The colouring is very peculiar, being generally reddish-brown 

 in the lower part of the colony, gradually merging into slaty-grey in the upper 

 parts. Patches of grey appear throughout the red in some of the colonies and 

 vice versa, while one colony from the Laccadives is almost of a uniform 

 brick-red colour. The surface bears longitudinal furrows which are sinuous and 

 sometimes almost spirally twisted, one being generally deeper than the others. 

 These extend into the secondary branches and even into one side of the twigs ; 

 the number diminishes with the size of the branches. 



The axis is very calcareous and cylindrical in form. It has an almost 

 olive-green colour at the base, gradually merging into a pale yellow in the smaller 

 branches. 



The polyps are disposed in a very indefinite manner. They are chiefly 

 lateral on the main stem or primary branches ; in the secondary branches they 

 are arranged almost all round. On the finer branches and twigs they occur for 

 the most part on two sides, but this rule is broken occasionally by the occur- 

 rence of polyps on all the four sides. The verrucfe are dome-like but slightly 

 flattened on the twigs. They are separated by intervals of about 1 mm. in the 

 branches, but their bases touch on the branchlets and give an undulating 

 appearance. They measure about 0"6 mm. in height and 1 mm. in diameter. 

 When the verruca closes over the retracted polyp an eight-rayed star is formed 

 by the eight lobes of the wall. The anthocodiaj are very minute and are com- 

 pletely retractile, the spicules being arranged transversely on the tentacles. 



The spicules of the coenenchyma are small, warty, and very diverse in form. 

 The following are a few of the more common types with measurements in 

 millimetres : — 



