BY E. A. BRIGGS. 



197 



7\-ophosome.- Colonies attaining a height of 40 mm. Stem 

 monosiphonic, geniculate, lax in growth, with rare and irregular 

 branches, which spring, with a long internode, from directly 

 beneath a hydrotheca. The branches reach a length of 20 mm , 

 and are divided into regular internodes, each of which bears a 

 hydrotheca towards its distal extremity. The internodes are 

 zig-zag, bending from one side or the other in gentle curves, 

 which follow the inner lines of the hydrothecse and give a genicu- 

 late form to the stem. In the older portions of the colonies, 

 owing to the great thickness of the perisarc, the nodes usually 

 become obscured, although a slight constriction immediately 

 distal to a hydrotheca generally indicates their position. In the 

 majority of the stems there is no trace of division into internodes. 



The hydrothecse are alternate and lie towards 

 the distal ends of the internodes, to which they 

 are adnate for about two-thirds of their length. 

 They are remarkable for their great depth and 

 for the length of the adnate portion. They are 

 not quite tubular, but reach a maximum diame- 

 ter at the point where they become free, taper- 

 ing slightly downwards until they end in a 

 rounded base, and less markedly towards the 

 mouth. The margin of the hydrotheca is 

 divided into three teeth, one adcauline, central 

 and projecting, the others forming an abcauline 

 lateral pair. The teeth are separated by shallow 

 embayments. The free adcauline wall of the Text-fig. l.—S'eritf- 

 hydrotheca is marked by several definite undu- 

 lations. The hydrothecal walls are strongly 

 developed. There is a tendency to regenera- 

 tion of the hydrothecse, many of the margins 

 being repeated twice or thrice. The colour of 

 the colonies is dark brown. 



Go7iosome. —The gonangia are borne on the stems and branches. 

 They lie along the anterior of these, and are so closely appressed 

 to the branch that the adcauline portion of the gonangium 

 becomes hollowed (jut into a longitudinal furrow to fit it, as in 



larella ritchiei, 

 part of stem, 

 with gonangi- 

 um, seen from 

 the anterior, 

 xl6. 



