54 



cm. in total length. It is granular in appearance and shows traces of a few 

 stolons at the base. 



The polypariiim is greatly flattened in one plane, roughly pentagonal in 

 outline, and practically entire, showing no breaks on the surface. It consists 



of four principal branches which all lie in 

 the same plane, two near the base of the 

 stem, and the other two just at the tip. 

 All over the main stem and branches smaller 

 liranches are given off", which by repeated 

 division give rise to the polyp-bearing twigs, 

 a slight tiattening being occasionally seen 

 at the point of division. Two of the lowest 

 branches are flattened, leaf-like structures 

 which almost surround the stem, leaving 

 only two small free spaces, in each of which 

 there is a small branch with a cylindrical 

 lower part and a triangular flattened up})er 

 part concave above. 



The polyps are arranged in groups of 

 four to eight, and occur also in small groups 

 or singly on the edges of the flattened 

 branches. They are i-ound in shape and 

 average 072 mm. in height and 072 mm. in breadth, and are placed at an 

 angle which varies from right to obtuse on stalks of about ] mm. in length. 

 The polyp-spicules are arranged in eight double rows, each of five pairs of 

 converging spicules, of which the uppermost pair are longest and project beyond 

 the polyp. The lower polyp-spicules average about 0'24 mm. in length, the 

 upper projecting spicules about 0-56 mm. On the aboral surface of the ten- 

 tacles there are two rows of small rod-like spicules. 



The Stiitzbiindel is well developed, one of its spicules may reach a length 

 of 3-2 mm. and project for a considerable distance beyond the polyp. 



Cortical spicules ; (n) In the stem there are numerous spindles either 

 curved or straight with numerous blunt spines on the surface. They may be 

 divided into two groups, the smaller averaging about OS mm. in length, the 

 larger about 2 mm. 



(fj) In the stalk there are spindles, clubs, three- and four-rayed forms and 

 numerous irregular globular forms, all of which bear numerous regularly 

 arranged prominent rough warts. There are in addition a number of forms 

 which vary from flattened spindles to discs, and some roughly triangular flat 

 plates which show a marked striation on the sui'face and are entirely free from 

 warts or spines of any description. The spindles average about 1 4 mm. in length. 



Fig. 28. D. pentagona. 



