104 MADREPORARIA. 



92. Porites West Indies x. 27. (P. Americana incertcc sedis scptima ct vicesima.) 

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



[Britisli Museum.] 



Description. — Tiic corallum creeps over the surface, the edges running out into h)hcR. 

 The njiper surface is rai.sed sparsely into small, low, round-topped cones, wliich slope concavely 

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

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

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



Tlic calicles vary from I'fi nmi. on the waves to 0'5 mm. in the valleys; they vary also 

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

 lamellate, as they ai'e also in th(> valleys, in which they are open, ragged, and incomplete 

 lattice-Works, witli 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. 

 Tiie 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 Hatter 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 astraioid Porites I have yet seen, and secondly in 

 the character of tlie calicles. Botli of them again an; explanate, that is, have creeping edges 

 with less m.arked growth of the central regions. Tliere 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 ])erhaps from the same locality. 



A comparison of this fonn with that which follows, shows that there is at least as nnuli 

 dilference 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. 



/*. Inegularly convex, PI. VI. fig. 7. Zool. Dept. 1906. 1. 1. 12. 



93. Porites West Indies r. 28. (P. Amrricana incertcr, xedis octava ct vicedma.) 

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



[British Museum.] 



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

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



