104 MADREPOKARIA. 



92. Porites West Indies x. 27. (P. Americana incertce sedis septima et vicesima.) 

 (PI. VI. figs. 6, 7 ; PI. XVII. fig. 9.) 



[British Museum.] 



Description. — Tlie corallum creeps over the surface, the edges running out into lobes. 

 Tlie upper surface is raised sparsely into small, low, round-topped cones, which slope concavely 

 down into broad, flat, shallow valleys. The valleys are filled with minute calicles, so crowded 

 that the walls are incomplete. The tops of the waves have larger, thick-walled calicles, so as 

 to look soft and foaming, contrasting strikingly with the appearance of the valleys. 



The calicles vary from 1'5 mm. on the waves to 0*5 mm. in the valleys; they vary also 

 in depth. The walls in the small intercalicular buds on the waves are membranous and 

 lamellate, as they are also in the valleys, in which they are open, ragged, and incomplete 

 lattice-works, with spiky edges. The network of the thicker walls on the wave tips appears 

 loose, open, and filamentous ; its lamellate character is almost confined to its vertical elements. 

 The septa are very thin and short, some longer than others, and not betraying any 

 strikingly radial arrangement. The columellar tangle is loose, open, and very irregular, so 

 that some calicles are very deep, while in others, strands of the columella rise up, making the 

 calicle look shallower. 



The colour of the unbleached stock is a warmish-brown. 



There are two specimens which differ in that the larger and flatter has slightly larger 

 calicles, PI. VI. fig. 6, but they agree first of all in the character of the eminences on the 

 surface, which differs from any other astrajoid Porites I have yet seen, and secondly in 

 the character of the calicles. Both of them again are explanate, that is, have creeping edges 

 with less marked growth of the central regions. There are signs also that the museum 

 acquired the two at the same time, which suggests that they were parts of one and the same 

 find, and perhaps from the same locality. 



A comparison of this form with that which follows, shows that there is at least as much 

 difference between the two as to justify the most timid of species-makers in giving them 

 different names. 



a. A large flat cake. Zool. Dept. 1906. 1. 1. 11. 



b. Irregularly convex, PL VI. fig. 7. . Zool. Dept. 1906. 1. 1. 12. 



93. Porites West Indies x. 28. (-P. Americana incertce sedis octava et vicesima.) 

 (PI. VI. fig. 8 ; PI. XVII. fig. 11.) 



[British Museum.] 



Description. — The corallum rises into a tall conical mound with rounded top, covered all 

 over with crowds of small mounds, almost of the same shape, and all rising vertically, but 



