292 



Pteroeides robustum, n. sp. 



Two large colonies represent this new species. 

 Specimen 

 Total length of colony 

 Length of rachis .... 



Breadth of rachis .... 

 Length of stalk ..... 

 Thickness of stalk .... 

 Number of pinnules .... 

 Number of rays ..... 

 Length of pro-rachidial margin of 

 largest pinnule .... 

 Breadth of insertion of largest pinnule 

 Breadth of largest pinnule . 

 Distance between pinnules . 

 This new species is included in Kolliker's 

 plate is basal, with a hint of a free space about the middle. 



Both the colonies are large, thick and very substantial. The stalk is spongy 

 and considerably swollen ; the pro-rachidial surface of the keel is very broad and 

 elliptical in shape. The pinnules overlap from either side and cover the meta- 

 rachidial surface, except near the base where a heart-shaped bare space is left. 

 The pinnules are large, thick and fan-shaped, some almost approaching the 

 form of a quadrant. There is a slight swelling or cushion at the pro-rachidial 

 insertion. The zooid-plate is large and conspicuous, reaching almost to the 

 polyp-zone on the meta-rachidial side. The rays vary in number in the two 

 specimens, in A, 18-19, in B, 15-17. They are composed of six to eight spines and 

 are very prominent, projecting slightly beyond the margin in a serrated edge. 

 The lower rudimentary pinnules are spatula-shaped and are inserted towards 

 the pro-rachidial surface, but the main pinnules are distinctly lateral. 



The polyps are situated on both surfaces in five or six rows which extend 

 almost half-way down the pinnules. There are also a few scattered zooids on 

 the upper surface of the pinnules. There are no limy needles either in the 

 polyp region or in the keel and stalk. 



The colour in spirit is creamy-white, but on the stalk and keel there are 

 bluish and brown spots. 



The same pathological condition of the rays as that referred to in F. 

 griseum is here present in specimen B. This species differs from P. (jritieum 

 in the fact that the polyps are not marginal ; it resembles F. sclilegelii in the 

 ventral shunting of the rudimentary basal pinnules. 

 Localities : A — Akyab. 



B — Andamans. 



