23° 



DISCOVERY REPORTS 



the cavity widens still more and becomes oval in section. The lining of the cavity is 

 smooth, but near the base of the colony there are stout bars extending at intervals across 

 the cavity and fused at both ends with the lining. In one specimen a few pocket-like 

 septa were found on the inner lining, near the base. Pocket-like septa are recorded for 

 the first time, but they are not homologous with the irregular partitions and pockets 

 found in C. dodecalophiis . 



At intervals along the sides of the stem and lateral branches are a number of short 

 branches bearing funnel-shaped ostia. A short branch bears three, four or five spines 

 and one or two ostia. The short branches enlarge by further branching of the spines 

 and the bifurcation of the ostia. In one case as many as seven ostia and fourteen spine- 

 tips have been counted on one small branch. The diameters of the ostia vary from 1-5 

 to 2-5 mm. and the number of marginal spines ranges from two to five (Fig. i). 



The short branches are not produced at regular intervals. On some branches they 

 are wide apart, and on others closely set. On one branch seventeen short branches 

 were counted in a 5 cm. length; while on another 

 only nine were found in the same length. 



The tips of the main branches also bear ostia 

 which are identical with those already described. 

 New ostia are formed by the growth of ridges be- 

 tween the spines. Ridewood (1918 «) has given a 

 detailed account of their formation, to which I can 

 add nothing. 



The spines are long, tapering and may be simple 

 or forked. The forking first appears as a knob of 

 spine rudiment at some point on the side, very 

 often near the tip of an old spine. It continues to 

 grow in length by the deposition of lamellae. Some 

 of the branches grow upwards, while others, de- 

 veloping horizontally, fuse with adjacent spines or 

 with the spines of adjacent short branches. 



Form B (PI. XXXIII, fig. 2). The short branches 

 are much larger and the spine longer and thicker 

 than those of Form A. Broadly speaking it may be 

 said that Form B is larger in every way than Form A. 

 The two forms are distinguished by the spines and 

 short branches; apart from these there is very Fig. 2. C./?o</^.o«/. A short branch showing 

 little difference in the general structure of colonies, the relation of the spines to the ostium in 

 The cavity is crossed by a few horizontal bars in FormB. 0, ostium ;c, cavity of coenoecium; 



^1 1 1 • 1 . 1 • 1 1 /), plate of coenoecium connecting spine d 



the basal region, but has no side pouches. ^ . , „ ^ . , . ^ ^ 



'- with wall of coenoecial cavity. 



The short branches of Form B are at least twice 



as long as those of Form A. Each branch has a main central ostium and one or two 



smaller ostia at the side, a little below the main one (Fig. 2). Typically the main ostium, 



