124 
A Iveopora viridis the upper margins of the walls of the calicles 
are relatively smooth and the rudimentary septal spines are slender 
and very deeply set. In A. spongiosa, on the contrary, the corres- 
ponding spines are short and thick and conspicuously developed 
near the calicinal orifice. Collected by the author in the neigh- 
bourhood of Thursday Island, Torres Straits. 
Tridacophyllia rectifolia, sp. nov. 
Corallum exceedingly fragile, forming a subeven hemisphere ; 
calicinal centres confined to the bottoms of the valleys, the 
external distal edges of the calicles even and uninterrupted, 
slightly perforate, not lacinulate ; valleys 5 - G centimetres wide; 
septa forming 3 or 4 cycles, subeven, their edges very finely 
denticulate, the distal termini of the first to third cycles slightly 
excurrent and somewhat echinulate. Diameter of entire corallum 
44 centimetres ; height 18 centimetres. 
Hob. New Hebrides. 
The great depth of the calicinal valleys, their perpendicular 
walls and subeven non-lacinulate distal edges, distinguish this 
species from Tridacophyllia lactuca , which in other details it most 
nearly resembles. The magnificent specimen constituting the type 
of this species, and of which a reduced photographic representation 
is appended, is contained in the Australian Museum, Sydney. 
