A REVISION OF THE GENUS STEGANOPOEELLA. 261 



I have found great difficulty in deciding whether the 

 encrusting species of Steganoporella which is common in 

 New Zealand deserves to be ranked as a species. For the 

 present I shall descinbe it as var. magnifica, a name which 

 I have found on two slides^ from Tongatabu, in the Busk 

 collection at the British Museum. 



In the diasrnosis I have chosen those characters which 

 are common to the two forms. I now give a description of 

 the typical form, indicating later the special characteristics 

 of var. magnifica. 



The Vincularian form grows from a mass of stout, chitin- 

 ous rootlets, which give off a number of cylindrical, unjointed 

 shoots, the largest of whicli, in the Cambridge collection, is 

 36 mm. long. The zooecia open all round these shoots. They 

 are arranged in the usual longitudinal rows characteristic of 

 Steganoporella, but their basal wall tends to be reduced 

 to a longitudinal line occupying the axis of the shoot. If 

 this result were actually arrived at the zooecia would be 

 three-sided prisms, all reaching the centre. There is, how- 

 ever, a considerable amount of irregularity in this respect, the 

 arrangement being indicated by fig. 30, which represents 

 part of a transverse section of the cylindrical shoot. 



The mode of growth of these groups of cylindrical stems, 

 united by a common mass of roots, does not seem to have 

 been described. Although I have not quite complete proof 

 as to the details, I have very little doubt as to what really 

 happens. The cylindrical stems are unbranched, except for 

 the fact that at their base, just where they join the mass of 

 rootlets, many of them give off a small offset. This offset 

 may reach a length of as much as about 5 mm. At this stage 

 the connection of the offset with the parent stem is becoming 

 weak, no doubt by an absorption of some of the calcareous 

 matter. The oifset is already directly connected with the tangle 

 of rootlets, and is ready to break olf as an independent stem. 



This offers an interesting parallel to the mode of jointing 



' A third slide, of uncertain locality, labelled by Mr. Busk as S. magni- 

 fie a, belongs to S. ni agniiabris. 



