64 THE VOYAGE OF H.M.S. CHALLENGER. 
developed than in the other, especially towards the apical parts. In both specimens 
many of the branches are fistular, being bored by one or more canals; and owing to this, 
and to the thinness of the branches and branchlets, and to the deep and crowded calicles 
which cover them, the corallum becomes comparatively light. 
Locality.—Kandavu, Fiji. 
Genus 2. Pocillopora, Lamarck. 
Pocillopora, Lamarck, Hist. Anim. sans Vert., ii. p. 273. 
3 Milne-Edwards and Haime, Cor., i. p. 301. 
#5 Duncan, Rev. Madrep., p. 47. 
The real affinities of this genus were first determined by Verrill, and confirmed by 
Professor Moseley, to whose research we are indebted for a more complete knowledge of 
the soft parts.’ 
Fourteen species of this genus were obtained. 
1. Pocillopora acuta, Lamarck. 
Pocillopora acuta, Lamarck, Hist. Anim. sans Vert., ii. p. 274. 
5 »,  Milne-Edwards and Haime, Cor., iil. p. 302, pl. F. 4, fig. 2. 
This species is extremely variable in the shape and thickness of the branches and 
branchlets and in the size of the calicles. The branches and branchlets may be subterete 
or slightly compressed and angular, acutely or nearly obtusely rounded at the end, thick 
and strong or rather slender, of very close and shrubby habit or elongated and sub- 
arborescent, of very dense and compact structure throughout or open cellular within. 
The calicles are always crowded, with the interspaces generally marked by fine lines 
which surround the calicles, towards the apical parts the interspaces become extremely 
narrow and the linear markings are absent; the diameter of the cups is generally about 
0°5 mm. to 1 mm. or more (in the type specimen of Lamarck the calicles are very small) ; 
the septa are more or less distinct especially in the apical parts, and are seen as minutely 
spinulous lines when magnified; the columella is distinct and forms a sharply convex 
spinulous projection elongated in the long axis of the branch. The surface is very 
‘sharply echinulate. 
According to these differences in habit and structure, individual specimens may 
appear specifically distinct from each other, while in a large series of specimens it will be 
found impossible to separate them by any constant character. 
A very interesting variety of the species was obtained at Banda ; in this the branches are 
often compressed, and are almost obtusely rounded above and of very shrubby growth ; the 
calicles are quite large and are scarcely crowded at the basal parts; the coenenchyma is 
1 Proc. Amer. Assoc. Adv. Sci., 1867. 2 Quart. Journ. Micr. Sci., new ser., vol. xxii., 1882. 
