INDIAN OCEAN PORITES 201 
201. Porites Ceylon (295. (P. Ceylonica quinta.) (Pl. XXX. fig, 6.) 
[Ramesvaram, coll. E, Thurston; British Museum.] 
Deseription.—The corallum grows out, as a flattened lobulated mass, with free horizontal 
base, from the side of an overturned mass of the same shape. Its upper part is divided into 
large fused knobs, each with its surface divided into much smaller lobules, Between the 
large knobs the cavities run down into the heart of the stock. The living layer on the out- 
side is some 8 cm. deep. 
The calicles are small, under 1 mm., deep, and angular; here and there, where walls are 
thick, they are neatly circular. The walls are mostly very thin, membranous, and porous; in 
the angles they dissolve into an open filamentous reticulum, The septa are very thin, 
smooth, and lamellate, symmetrically arranged, and spring rather high up from the walls as 
far as the septal granules, after which they drop down. The pali rise as high as the septal 
granules, and surround a large fossa with a ring of eight, only the four lateral principals being 
really developed. The columellar tangle is well developed, and reticular. The central 
tubercle is thin, and flattened in the directive plane. In the calicles round and under the 
rim, the walls are a thick, ragged, open, filamentous reticulum ; the septa tend to be echinulate. 
The colour is light brown; there is no visible section. 
In the observations on No. 4, it is suggested that laminate trabeculee may be associated 
with great rapidity of growth, the elements then being smoother and the walls taller, and if 
so this might account for the differences between this coral and No, 4, But even then it is 
not easy to see how these variations would account for the differences in growth-form, The 
form No. 7 has calicles somewhat of the same pattern as those of Nos. 4 and 5, but with very 
tall walls, the growth-form being also entirely different. 
a. Zool. Dept. 88, 11. 25. 7. 
! 202. Porites Ceylon (g2)6. (P. Ceylonica sexta.) (Pl. XXX. fig. 7.) 
[Ramesvaram, coll. E. Thurston; British Museum. ] 
Description.—The corallum forms perfectly smooth, rounded, or ovate masses, which 
appear to roll over and find attachments to loose objects, enveloping foreign bodies by 
thick creeping edges of the living layer. The gradually dying sides are covered over by a 
conspicuous white epithecal film. 
The calicles are 1°25 mm. (with frequent double calicles, 2 mm.), flush with the surface, 
symmetrical, and star-like. The walls are a mere thin, straggling, polygonal thread, irregularly 
joining the ends of the septa, often interrupted, and not appearing at the surface at all, At 
2D 
