17 



Nephthya tenuispina, n. sp. 



Several small but complete colonies attached to pieces of rock, the largest 

 is 3 cm. in liei<;lit. Kioni a si)rea(ling base, 1"8 cm. in diameter, the main portion 

 arises, but this soon gives origin to several long, sliglitlv tapering lobes. These 

 diverge in all directions, some even growing downwards. Polyp-bearing lobes 

 occur all over these secondary branches. A cross-section through one of the 

 larger lobes presents a radiate structure, the canal walls passing from the 

 centre to the circumferenc^e, but this becomes ob.scure in the older portions by 

 the development of smaller canals towards the periphery. The outer wall is 

 tough and rigid and is densely filled with long spiny S[)indles. 



The polyiJs are borne on catkin-like out- 

 growths of the larger lobes, but on the main stem 

 they occur in groups separated by considerable 

 intervals — seldom singly. 



The surface of the whole colony is covered 

 with long, straight or curved spindles, generally 

 arranged in groui)s and disposed longitudinally. 

 On the smaller lobes, where the polyps are more 

 crowded, the arrangement is much more irregu- 

 lar, but here also the grouping is a marked feature. 



The polyps are almost 2 mm. in length, the 

 stalk being slightly over 1 nun. The " StUtz- 

 biindel " consists of about six long thick spindles, 

 grouped into a sheaf, projecting for a considerable 

 di.stance beyond the origin of the body of the Fig. 8. Nephthya tenuispina.n.sp. 



1 ^ — The top of two branches, 



1 ^I* enlarged about eight times. 



The polyp stands at right angles to the stalk 

 and is directed towards the colony, but when the tentacles are fully retracted 

 the oral part projects downwards. Spicules longitudinally arranged cover the 

 whole surface, but there is a hint of eight groups at the base of the tentacles. 



The spicules are straight and curved, spiny and warty spindles and present 

 the following range of measurements length by breadth in millimetres : — 

 1-0 X 0-15 ; 1-5 X 0-12 ; 09 x 004 ; 07 x 003 ; 03 x 002. 



This species is remarkable for the great slenderness of the spindles. 



Locality : Andamans. Marine Survey. 



