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. 



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 VII. G G. 



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. 



Ccenosteum of Allopora profunda, n. sp. 



The ccenosteum (PL I. fig. 6, a) 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 



