62 THE VOYAGE OF H.M.S. CHALLENGER. 
the further disposition of which has been already described. The immediate under 
surface of the gastrozooid is devoid of canal offsets, and is attached to the centrally 
placed style. 
The histological structure of the zooids in the present species of Stylaster closely 
corresponds with that already described as existing in those of Sporadopora dichotoma. 
The gastrozooids in the present form, and their tentacles, are so short that it seems 
improbable that these zooids are able to emerge from the summit of the gastropore in 
the expanded condition of the coral. The dactylozooids probably become, when active, 
long and filiform, and acting as tentacles bend inwards to supply the gastrozooid with 
food. wa) 
Gonophores.—Only male specimens of Stylaster densicaulis were obtained. Each 
male ampulla contains two or three ovoid gonophores, which are attached to large 
offsets of the ccenosarcal meshwork at one end of their longer axes. They have an 
internal spadix, and in finer structure seem to differ very little from those of ‘Spora- 
dopora. They are shown as seen through the transparent walls of the ampullar sacs 
in Plate VIL. GG. 
Allopora, Ehrenberg. 
To this genus I have referred a coral dredged off the mouth of the La Plata, on 
account of the very considerable irregularity with which the pore systems grow out 
from one another. The coral seems to represent a species hitherto undescribed, which I 
term Allopora profunda. 
Coenosteum of Allopora profunda, n. sp. 
The ccenosteum (Pl. I. fig. 6, @) is composed of a stout stem bearing numerous 
branches. The branches ramify to some extent in the same plane, so as to form a sort of 
flabellum ; but this flabellum is curved considerably in the direction of its height, and 
its lateral margins are also bent over sharply towards the same curved face. The main 
stem has a sinuous course, and the branches are all more or less curved in direction. 
The stem and branches are. oval in transverse section, being flattened in the plane of 
the flabellum. The ccenosteum is white, and its surface is minutely granular. The pores 
occur in regular cyclo-systems ; when young they project from the terminal branchlets 
in the form of small cylindrical masses, which are slightly expanded in diameter at 
the free extremity. These cyclo-systems show a tendency to a regular alternate 
arrangement, the base of each system abutting on the side of the preceding, and the 
axes of the systems being inclined to one another at an angle of about 45° in the 
