48 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus Callozostron,^ Perceval Wright. 



Callozostron, Perceval Wright, Narr. Chall. Exp., voL i. p. 691, 1885. 



In addition to the characters of the subfamily, of which this is the only genus, the 

 ccenenchyma is thin and covered with large scale-like spicules ; owing to the extreme 

 crowding of the polyps on the axis, this is chiefly to be seen on the ventral ridge-like 

 portion of the colony, from which the polyps diverge. The polyps are encased in several 

 (six to seven) rows of imbricated scales, the last row of which, below the opercular scales, 

 consists of four to eight scales which are furnished with very long spines. These form a 

 pre-opercular calyx. 



Callozostron mirabilis, Perceval Wright (PI. X. figs. 1-5 ; PI. XX. fig. 1). 



Callozostron mirabilis, Perceval Wright, Narr. Chall. Exp., voL i. p. 69, figs. 234, 235, 1885. 



The axis in the imperfect specimen dredged of this deep-sea form is about 280 mm. 

 in length, it is extremely flexible, and nearly 20 mm. in widest diameter. The colony 

 strongly reminds one at first sight of some gigantic Annelid. The axis is feebly 

 calcareous, consisting of a central portion around which are a variable number of canals, 

 apparently corresponding to the number of polyps around the axis. These canals vary 

 in size, the smaller being on the dorsal aspect of the axis, i.e., that portion opposite to the 

 space free of polyps, and where the younger polyps are. The central portion of the axis 

 appears in thin sections, which have been decalcified, to be altogether calcareous, while 

 the rest of the axis is membranous, with calcareous, amorphous particles interspersed. 

 Around the large canals numerous nutrient canals form a network. The polyps are 

 very prominent, from 6 to 7 mm. in height from their base where it joins the axis to 

 the tip of the epicalycine spicules. They are about r5 mm. in diameter, which is 

 nearly the same throughout. The body of the polyp is completely encased in rows of 

 imbricating scaly spicules. The tentacles are completely retractile, and covered with six 

 to eight overlapping scale-like spicules, the outer row have frill-like everted edges ; below 

 these are four to six triangular scale-like spicules, with apices projecting in the form of 

 very long spines, forming a pre-operculum. The polyps increase by lateral budding, so 

 that they are in clusters of from one to four. 



In the ccenenchyma the spicules are flat, scale-Hke, some angular, others orbicular, 

 some few flat spindles ; all of the spicules are serrated on their edges, and are 

 tuberculated. 



Measurements, 0-404-0-504 ; 0-306-0-602 ; 0-602-0-4; 0-804-0-708; 0-704-0-8; 0-6 

 by 0*4 and 0-4 mm. 



The spicules of the polyps are scale-like, tri- and quadrangular, sometimes slightly 



