76 MADREPORARIA. 
The palic formula seems to be mainly D, fig. 3 (p. 19), with five principals and one small 
directive. The columellar tangle is large and dense, appearing high up among the intra-calicular 
skeletal elements. 
This Porites is quite remarkable in the variations in the walls. 
+ Zool. Dept. 1904. 10. 17. 33. 
52. Porites Ellice Islands qy13. (P. Hlliciana tertiadecima.) 
(PL. VII. figs. 4,5; Pl. XIII. fig. 22.) 
[Funafuti, coll. J. S, Gardiner ; Cambridge University Museum. ] 
Syn. Porites arenosa (partim) Gardiner (non Esper) Proc. Zool. Soc. (1898) p. 272. 
Description.—The corallum is massive, the surface smooth, with round, low waves, but the 
complete form is unknown. 
The calicles are 1 mm. in diameter, nearly flush with the surface, varying from angular 
to sub-circular, owing to the wall angles being often reticular. The walls (Pl. VII. fig. 4) over 
the greater part of the surface are thin ridges, finely zigzag, membranous, with very scanty 
perforations and denticulations. These ridges are raised slightly but uniformly above the 
surface. A variation on this type of wall appears (Pl. VII. fig. 5) on one of the sides of the 
stock (see the asterisk on Pl. XIII. fig. 22); it is reticular but flat-topped, and flush with the 
surface, the septa in this case showing as thin radial strize running halfway over the wall, 
and ending as if against a zigzag ridge, which, however, is no longer visible at the surface. 
Seen from above, the angles of the thin normal walls, when thickened into a reticulum, 
appear as a very fine open filamentous network (Pl. VII. fig. 4), but sideways the network 
is seen to consist of vertical lamine. The septa appear faint, thin and incomplete; but 
present in the full formula. The four principal pali contrast strongly with the septa, being 
conspicuous V-shaped granules; seen sideways they are smooth rods which rise high, almost 
to the level of the walls. The other four pali are variously developed, sometimes present, 
sometimes absent, and always smaller than the principals. A very minute central tubercle 
is nearly as tall as the pali; and deep down among the open interseptal loculi a symmetrical 
columellar tangle can be made out with radial strands running to the centre. 
In the vertical section the laminate character of the skeleton is clearly seen in the 
walls and septa; in transverse section the rings of interseptal loculi can be always traced. 
There is certainly some affinity between this coral and that last described. The fact 
that both produce lateral calicles with striated walls, elsewhere hardly known in the genus, 
is significant. But beyond this bare fact the skeletal details are not alike (cf. Pl. VII. fig. 2 
with fig. 4, and fig. 3 with fig. 5), 
The only specimen is in the Cambridge University Museum. 
