TURBIXAELE FOLIATE. 51 



conspicuo\is development of the ridge-and-furrow system. The reticulum may be composed of 

 threads or bands. 



Owing to the small depth of the fronds, the stocks do not rise to any height, but spread 

 laterally, the dead portions being grown over by new fronds. 



There are four specimens wliich apjiear to belong together, although there is some doubt 

 as to wlietlier they might not be divided into two species. 



The specimens c and d differ slightly from the type. In the former (c) individual calicles 

 project to a great height and tlien bend, giving rise to a secondary polyp ; further, whereas tlie 

 margins of tlie calicles in the type are sharp and clearly defined, the reticulate structure of the 

 ccenenchyma being very fine, in this specimen the reticulum of tlie coenenchyma is coarse, 

 and the thin margins easily crumble away. 



The specimen (rf) is a small nodule with the same character of calicle, but with the 

 reticulum of the coenenchyma very massive and close, the nodule being almost like a solid 

 stone. 



There is another specimen (from Diego Garcia, now labelled y. ^Zo&MZ«m) which resembles 

 this species in general characters of the calicles, but it is a large globular mass, and lias, for 

 the sake of consistency, been transposed to the glomerate group. Its resemblance to T. irre- 

 gularis, which here and there forms encrusting nodules among the fronds, combined with 

 the fact that other glomerate specimens bear a close resemblance to certain other types, inclined 

 me at first to believe that all the glomerate Turbinarians were but accidental massive varieties. 

 It is quite possible that such massive varieties may occur, but the evidence in favour of a 

 distinct glomerate type of growth compels us to place all globular forms apart, unless we have 

 clear proof that any particular specimen is such an accidental variety. 



The specific name irrcrjxdaris was suggested by the remarkable fact that the fronds fuse 

 face to face, wliich must involve the continual destruction of the polyps. This deliberate 

 sacrifice of a percentage of the individuals does not, however, affect the vigorous growth of the 

 colony as a whole. 



a. Mauritius. (Type.) 



h. Mauritius. 

 c, d. Locality not recorded. [Register Nos. 93. 7. 1. 7 ; 96. 2. 11. 1.] 



Species 29. Turbinaria robusta. (ri. XI. ; V\. XXXII. fig. 5.) 



Description. — Fronds more or less erect, deep, upper edge freely bent, often wavy, 

 and not crowded, frequently fused back to back, forming tall flat processes, or else hollow 

 cylinders. Margin stout, about 4 mm., with conspicuous row of large round calicles developing 

 along the edge. 



Calicles tall, barrel-shaped, projecting on prominences ; but on the fronds, the aperture 

 only projects so as to look outwards and upwards; the ventral edge is, however, raised 

 somewhat above the ccenenchyma. 



The aperture is round or round-oval, or at times almost oblong, surrounded by a thick 

 margin. The septa (20 to 24) are either suddenly differentiated out of tiie margin as thin 

 lamella;, or only gradually, and, seen from above, are then wedge-shaped. They do not reach 



n 2 



