166 MADEEPOEARIA. 



of 1 to 1'5 cm. ; these consist of a stout, elongate, axial corallite, provided with nariform buds, 

 excepting on the inner aspect, which is nearly always devoid of corallites, excepting on the 

 distal part of the more elongate branches. Immersed corallites are chiefly confined to the 

 basal parts, and are usually small (0'7mm.). Star imperfect, usually only the directive septa 

 are recognizable. Corallum porous near the surface, but dense within ; surface strongly and 

 closely echinulate ; wall echinulate, the echinulations are often arranged in longitudinal rows 

 near the base of the cylindrical corallites situated near the apex, but not in other situations. 



Pacific Ocean : Great-Barrier Reef. 



219- ) Types. 



221 to 223. J ^^ 



224. (Var.) 



234. (Subcespitose.) 



B. Corallum forming a subcomplanate reticulum, vnth short twigs on the upper surface. 



177. Madrepora cancellata. (Plate XXXII. fig. C.) 



Corallum prostrate and reticulate ; branches about 1 cm. diameter, with postero-lateral 

 conical corallites, which may form twigs 1'5 cm. long and 5 mm. thick. The only other 

 corallites on the under surface of the reticulum are immersed or subimmersed, quite distant 

 and scattered. On the upper surface of the branches the corallites are mostly broad-nari- 

 form, with the wall often much thickened and the margin rounded ; length 2 to 3 mm., 

 diameter 2 to 2*5 mm. At irregular intervals certain corallites become tubular and proliferous, 

 and may then form arched twigs of variable length up to 2 cm. Axial corallites conical, 

 surrounded by scarcely prominent radial corallites with wide aperture ; diameter 3 mm., and 

 2 mm. exsert ; star well developed, the directive septa usually broadest. In the radial 

 corallites the directives are very broad and stout, but all the other septa (usually 10) are quite 

 narrow. Corallum very dense; surface and corallite-wall very closely echinulate. 



Louisiade Archipelago. 



a. Coralhaven, Louisiade Archipelago, 15 fathoms. 51. 9. 29. 39. (Type.) 



178. Madrepora pumila. 

 Madrepora pvmUa, Verrill, Comm. Essex Inst. 1866, vol. v. p. 23. 



" Corallum low and spreading horizontally near the bottom, the branches spreading from 

 one side of the coral. These are openly reticulated, occasionally coalescent, crooked and 

 irregular, flattened from above, giving ofE from the sides and upper surface short, irregular, 

 scattered branchlets, many of them consisting only of a terminal cell, with one or two small 



