52 



The stalk is thick and fairly rigid, measuring 27 cm. in length and giving 

 oif a number of short stolons at the base. 



The polyparium is large, much flattened, regularly oval, and presents a 

 very compact appearance owing to the numerous small branches wliich raise all 

 polyps more or less to the surface. It is further characterised by the great 

 development of flattened bi-anches at its lower end. At the upper end of the 



stalk two large flattened leaf-shaped 

 branches or folds almost surround the 

 stem, forming a collar to the upper part 

 of the stalk and leaving only two small 

 open spaces. They are very long, and 

 the ends of the folds are curved upwards 

 towards the apex of the colony. In the 

 angle between them a smaller branch 

 arises with cylindrical stalk and a flat- 

 tened, three-cornered upper portion which 

 stands at right angles to its stalk, the 

 beautiful correspondence between its free 

 edges and those of the larger neigh- 

 bouring branches giving it an appearance 

 somewhat like that of a bone suture. 

 Above the small space on one side an- 

 other flattened branch arises, but it is 

 reduced to a small narrow band, for directly above it two other flattened branches 

 arise which come into contact almost above the middle of it. On the other side 

 the single flattened branch is absent, there being only the two similar upper 

 ones. Above this numerous branches are given off', filling out the regular oval. 

 The polyps are arranged in small groups, commonly of seven individuals, 

 but occasionally groups of four and also of nine are found. On the edges 

 and upper surface of the lower flattened branches they occur singly or in small 

 groups of four to five. The polyps, which are placed at an olituse angle on a 

 stalk measuring about lo mm., are low, egg-shaped bodies, slightly flattened, 

 with an average height of 048 mm. and a breadth of 0"72 mm., the greatest 

 breadth being dorso-ventral. The spicules are arranged in eight double rows, 

 in each of which there are four to five pairs of converging spicules ; the upper- 

 most pair are of unequal size, the larger projecting 43eyond the polyp for a 

 considerable distance. The spicules are flattened spindles, either straight or 

 curved, with simple spines, which on the projecting part of the longest spicules 

 are directed towards the tip. The lower spicules average 0"33 mm. in length, 

 while the projecting spicules may reach a length of 072 mm. and may project 

 for a distance of 0'39 mm. 



Fig. 27. D. foliata 



