310 



the bluish-green polyps stand out in marked contrast. The stalk is smooth and 

 hard and bears two swellings, one close to the base, the other a short distance 

 below the rachis. The axis extends from end to end of the colony and is very 

 distinctive. In the lower part of the stalk it is flexible and almost cylindrical, 

 often curved back within the ccenenchyma. In the upper part of the stalk it is 

 four-cornered with a groove on each surface, those on the pro- and meta-rachidial 

 surfaces being much deeper than the other two. These are continued through- 

 out the whole length of the rachis but the para-rachidials disappear, and are 

 replaced by a characteristic honey-comb structure in the recesses of which the 

 polyps are embedded. This gives a distinctive contour especially to the younger 

 colonies. 



In one of the specimens the stalk has been broken oft' at the base of the 

 rachis and the fracture has been quite overgrown by the ccenenchyma. 



Large ova are present in several of the more mature colonies. 



The following are some of the types of spicules with measurements in 

 millimetres : — 



(a) Eough plates, 0-1 x 0-03 ; 0-09 x 0025. 



(b) Smooth rods, 0-08 x O'Ol ; O'O? x 0-075. 

 (f) Minute crosses, 0-04 x 0-04. 



From the Pei'sian Gulf there are also a number of very young stages 

 (largest 25 mm. long) in which the characteristic type of axis is visible through 

 the thin ccenenchyma of the rachis. In these the stalk is often three times as 

 long as the rachis and tapers to a fine point. The rachis itself often terminates 

 conically. 



Localities : Andamans ; Persian Gulf, 3 fathoms. 



Lituaria hicksoni, n. sp. Plate IX. fig. 2; Plate VI. figs. 7 and 8. 



We have referred to Lituaria several beautiful and in many ways unique 

 colonies which show the essential features of the genus, but differ in certain 

 details. The axis tapers towards the top of the rachis, and is without the char- 

 acteristic honeycomb structure seen in L. ■phalloides ; and the types of spicules 

 are slightly different. As these differences do not seem to us to justify the 

 establishment of a new genus, we would emend the diagnosis, founded on a 

 single colony, so as to include our specimens. 



The following; are the measurements in millimetres of some of the colonies ; — 



The axis extends throughout the entire length of the colony. Towards 

 both ends it tapers slightly and is almost cylindrical, but in the rachis it is four- 



