INDIAN OCEAN PORITES. 197 
Seven specimens from the Pearl Bank, and all growing on the Pearl shell 
(Margaritifera vulgaris). 
Three specimens from the sub-fossil reef described by Mr. Thurston in the 
Bulletin of the Madras Government Museum, No. iii, 1895, pp. 91-93. 
The Ramesvaram Series—These corals without exception are massive, but show the 
following strange method of growth. The earliest colony starts from a small base, often a 
branch of a Madrepora or a piece of a dead Astreid.:_ Above this base it swells into a knob 
continually increasing in size without being able to widen its base of attachment. This 
knob eventually becomes top-heavy and breaks off. Fallen on its side, the stock then presents 
a solid and more extensive base for its own future growth; upon and above this fallen stock 
the colony both rises in height and swells out rapidly in circumference. These lateral 
swellings often stand out parallel with the substratum on all sides like a flat resting base, or 
even droop down on all sides like a thick curtain, but in neither case does the colony again 
adhere to the substratum. This applies to all the forms from No. 1 to No. 9, even though 
their calicles show them to be very different corals, and though their growth-forms are also 
very different. It would be interesting to ascertain what it is in the character of the surface 
which prevents these corals from adhering. The phenomenon at once suggests the presence of 
sand or mud, 
With regard to the division and grouping of the specimens themselves, we are met: by 
many great difficulties, owing to the variations of the calicles on one and the same specimen, 
and of the details of growth-form in the different specimens. We have fairly clear evidence 
that these two—calicles and growth-form—are largely interdependent, but which comes first 
and conditions the other we do not know. 
197,.‘Porites Ceylon (221. (P. Ceylonica prima.) (Pl. XXX. fig. 8; Pl. XXXV. fig. 29.) 
[Ramesvaram, col].. E. Thurston ; British Museum. ] 
Description.—The corallum is a large, flat, oval mass, detached and resting on one side. 
The surface is lobulate or dimpled, according as the low rounded eminences, which are 3 cm. in 
diameter and 0°5 em. high, are distinct or crowded. The living layer is 14-15 cm. deep and 
bends 5-6 em. under the flattened base. The specimen is 30 em. long, 20 cm. broad, and 
16 em. high. 
The calicles are 1*5 mm. across, flush with the surface, faintly pitted and inconspicuous. 
The walls are hardly raised, and consist of a fine very delicate reticulum which is neither 
filamentous nor flaky, with small pores. The reticulum is often regular, consisting of a jagged 
irregular median ridge with synapticular walls on each side of it, and separated from it by 
regular rows of pores. Down the sides and on the under surface, the reticulum is irregular, 
being thicker and of stouter elements with smaller pores. The septa are very short, and lose 
themselves in an immense columellar tangle, in the structure of which traces of concentric 
