244 



DISCOVERY REPORTS 



position. In the basal regions the spines are long, stiff, thick and tapering, while 

 towards the tips thej' are slender, shorter and very pliable. 



The main stems are 3-7 cm. across in the thickest parts, but the width of the apical 

 regions is not more than i to i-8 cm. The older parts of the coenoecium are dark reddish 

 brown and very opaque, so that the zooids inside cannot be seen, even by strong trans- 

 mitted light. Nearer the tip, the dark mass of zooids can be seen distinctly through the 

 light brown semi-transparent coenoecium. Usually the main stem grows vertically, 

 producing secondary branches from its sides. A single stem 8 cm. long may bear as 

 many as four to six branches. Branches are produced on all sides of the stem, but if the 

 main stem is horizontal they are found only on the upper side. Entangled among the 

 branches arenaceous tubes of Polychaetes, calcareous branches of Polyzoa, Ostracods and 

 small Ophiurids are often found. Big sand particles and masses of mud are also deposited 

 locally. 



The colonies are a meshwork of bars and spines constructed as in Form A, but more 

 elaborately, due to the greater length and thick- 

 ness of the colonies. The spines of the tip of the 

 branch are directed upwards so that the growth 

 of the spines, accompanied by the formation of 

 lateral bars between them, increases the length 

 of the branch, while the production of lateral 

 bars between the obliquely directed spines on 

 the sides increases its thickness. 



Although the meshwork is very distinct in the 

 apical regions, the bars and spines lose their 

 identity below by the addition of coenoecial sub- 

 stance around them. As in Form A, spaces in the 

 surface meshwork form the openings for the 

 zooids. 



A hand-cut longitudinal section, from the 

 interspaces of which the zooids are carefully 

 washed out, shows the structure of the coenoecium given in Fig. 4. Spines A and B 

 grow in opposite directions from the axial part of the branch. A lateral bar between 

 them at the base results in the formation of a closed mesh which is at first rectangular. 

 Since these two spines diverge, if a second bar is formed between them above the first 

 one, the space enclosed would be much larger than the first one, so in the middle of the 

 first bar the rudiment of a new spine is laid down, which grows up as spine C. Between 

 A and C and C and B two bars are formed simultaneously, thus enclosing two spaces 

 which are of almost the same size as the one below. As the spine C continues to increase 

 in length one or two more bars may be formed between A and C and C and B, without 

 appreciably increasing the size of the spaces enclosed. Now the spines D and E are 

 produced. These may be formed in the same way as spine C or may arise as branches 

 from the side of ^ or £ ; but whatever the origin they serve the same purpose as spine C. 



Fig. 4. C. kempi. Structure of the meshwork. 



