96 MADREPORARIA. 



84. Pontes West Indies x. 19. (P. Americana incertce sedis nonadecima.) 

 (PI. V. fig. 8 ; PI. XVI. fig. 1.) 



[British Museum.] 



Description. — The corallum rises from a thin oblique stem (? overturned) from 1 to 1 • 2 cm. 

 tliick into a rapidly expanding cluster up wavy, forking, and gradually thickening stems ; 

 it is some 12 cm. high and 15 cm. in diameter of its nearly level top. The great number of 

 undivided stems are due to rapid forking, without trace of regular dichotomy. They are very 

 crowded but free, that is, do not fuse. In thickness they vary greatly, and wave about, some- 

 times digitiform, sometimes flabellate or irregularly swollen. The living layer is confined to 

 the tips, is only 2 • 5 cm. at the deepest, and each separate tip is either a small single knob or 

 swelling, flattening, and dividing quite irregularly, putting out divisions almost wherever there 

 is room for them. An epithecal film creeps up over dying edges. 



The calicles are small, average about 1 mm. in diameter, and shallow, though with 

 a skeleton sufficiently open as to appear deep. The wall over all the tips is delicately 

 membranous, and raised cup- or funnel-shaped above the surface ; lower down it is a thin wall- 

 thread, here and there becoming reticular, with flaky filamentous elements and smooth round 

 pores or meshes. The septa are thin and delicate where they actually leave the walls, but 

 soon swell into granules. They are very perforated, and lower down project as echinulate rods 

 joining the pali and the columellar tangle ; seen from above, the typical septal formula can be 

 made out ; seen close, the skeleton is too broken up into an apparent confusion of frosted or 

 echinulate granules to show any symmetry. The pali rise up from the tangle as very small, 

 irregularly star-like granules, varying in number according to the development of the directives 

 from five to seven. There is usually a smaller central tubercle rising with the pali from an 

 open, somewhat scanty, central tangle. The tubercle rises at times from systems of spokes of 

 this tangla The interseptal loculi, in spite of the echinulate sides of the septa, are large and open. 



In .section, the axial strand is of stout streaming network, showing the outlines of calicles 

 very distinctly ; it is not very extensive, and changes gradually into a stout, radially streaming 

 reticulum, in which trabeculae are fairly conspicuous. 



The colour of the unbleached coral is a rather deep warm buff. 



This is another of the West Indian Porites in which the uprisings tend to enlarge 

 as they rise, causing great irregularity in the ordinary dichotomous brandling, see Table III. 

 p. 136. Tlie great width of the cluster rising from so small an attachment is interesting. It 

 must have very soon become top-heavy. All the knobs into which its colony is broken up 

 reach about the same level. The method of growth should be compared with that last 

 described. It is very different from either the clavaria or furcata of Lamarck, while again, 

 they differ from one another by characters which most systematists, working on the ordinary 

 lines, would claim to be specific. 



a Large stock. 1906. 1. 1. 4. 



b Broken from a, and with two fragments, one of which is bleached. 1906. 1. 1. 5. 



