760 J. SXANLEY GARDINER. 



VI. Genus Mussa. 



7. Mussa corymbosa (Forsk.). 



Mussa corymbosa and cactus, Dana, pp. 177 — 8, vii. 1. M. corymbosa, Ed. and H., 

 p. 333, and Klz., p. 6, i. 4 and 9. M. cactus, Gard., p. 737. 



Locality. Sparingly on lagoon reefs and in holes of the reef-flat in the Maldives (six 

 specimens). Colour, a brown padded edge, surrounding a green peristomial valley. 



VII. Genus Symphyllia. 



8. Symphyllia sinuosa (Q. and G.). (PI. LIX. figs. 1, 2 and 3.) 



Meandrina sinuosa, Quoy and Gaimard, Voy. de I'Astr., Zooph., p. 227, PI. XVIII. 

 figs. 4 and 5 (1833); Symphyllia sinuosa, Ed. and H., ii. p. 370, and Gard., p. 738. 



I refer seven specimens to this species, and I have two further specimens from Rotuma 

 and the Singapore region before me. They show clearly that the genus is formed by the 

 fusion together of series such as are found in Mussa. The species is simply a massive Mussa 

 closely related to M. corymbosa. 



Internal structure. The dividing wall of the series in all the sj^ecimens j)ossesses a 

 distinct furrow or groove. In parts of some of the colonies it is a valley in the upper edge 

 of the wall, but over the greater part of their surfaces is merely a narrow deep notch between 

 the outer edges of the septal plates (septa + costae), which are only secondarily continuous 

 between the calicular rows. This can be clearly seen from the surface owing to the fact that 

 the septa of neighbouring rows are seldom exactly opposite to one another, and that the 

 thicker septa rather tend to alternate than lie opposite. In section it is clear that the septa 

 are not continuous, and in places one can distinguish between their outer edges a thin, ver- 

 tically rising plate. The latter is much fenestrated, and is incomplete ; it may be a secondary 

 formation, but appears to be continuous right down to the epitheca of the colony, and in 

 my view represents the remains of the fused epitheca of neighbouring rows. The exothecal 

 dissepiments are 1'5 — 3 mm. apart in accordance with the thickness of the wall; they are 

 not continuous between the tlieca of neighbouring rows, but are arched, convex side upper- 

 most, from the theca to the centre of the wall, i.e. to the fused epithecal line above mentioned. 

 The morphology appears to be the same in all the specimens, but there is great variation in 

 the thickness of the walls (2'.5 — 8 mm.), and in the thinner their structure may be almost 

 obliterated so that they appear relatively solid. The endothecal dissepiments are lightl}' arched 

 from the theca to the columella ; they are thin and often form large vesicles about 2 mm. 

 broad by 5 — 10 mm. long. The septa may be almost complete or much fenestrated, near their 

 edges passing into flattened, upstanding plates, the innermost and smallest of which form the 

 columella. 



Variation. The specimens in their internal structure show little variation except what 

 is dependent on the thickness of the walls and the distinctness of the furrows, both already 

 referred to. There are two classes of septa, (a) coarse, upstanding, 3 — 5 mm. exsert, 1 — 2 mm. 

 thick over the theca, with 1 — 3 great pointed teeth near their upper edges, passing internally 

 into blunter lobes or relatively fine teeth, and (b) fine, not more than 2 mm. exsert nor 

 1 mm. thick, closely set internally with fine pointed teeth. In the Rotuma specimen there 



