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



The opercular scales are small discs, and are not capable of completely closing the 

 opening of the calyx. 



The calyx scales are rectangular, very broad and flat, with an upper smooth edge 

 and a toothed lower edge ; the edge of that scale which is laterally covered by the next 

 is likewise toothed. Near the base the scales become somewhat higher, and their form 

 irregular. Height to breadth, 0-12-0-26 ; 0-13-0-29 ; 0-15-0-3; 0-13-0-26 mm. 



The opercular scales are short, relatively broad little plates, which appear 

 truncated, with the exception of the dorsal ones, which are pointed at tlie end. 

 Height to breadth, 0-06-0-07 ; O-ll-O-l ; 0-12-0-1 mm. The scales of the 

 coenenchyma are irregularly triangular or polygonal, 0"26— 0'14 ; 0'27— 0"12; 

 0'17-0'13 mm.; in the lower layer they form warty spindles which are at times 

 forked, 0-09 and 0*07 mm. long. 



Habitat. — Station 308, ofl:^ Tom Bay, Patagonia; lat. 50° 10' S., long. 74° 42' W.; 

 depth, 175 fathoms ; bottom, mud. 



Primnoella australasiw, Gray (PL XYHI. figs. 1, la ; PI. XXI. fig. 15). 



Primnoa aiisiralasiee, Gray, Proc. Zool. Soc. Loud., 1849, p. 146, pi. ii. figs. 8, 9. 

 Primnoella amiralasia;, Gray, Aun. and Mag. K^at. Hist., ser. 2, vol. v. p. 510, 1850. 



„ „ Gray, Proc. Zool. Soc. Lond., 1857, p. 286; 1859, p. 483. 



„ „ Gray, Cat. Lithophytes Brit. Mus., 1870, p. 50. 



„ „ Verrill, Bull. U.S. Nat. Mus., 1876, No. 3, p. 76. 



Several specimens of Primnoella from the Challenger collection may lie referred to 

 this species. The numerous cells which constitute the whorls and are provided with 

 two dorsal longitudinal rows of scales coming together at an angle, easily characterise 

 the species. The figures of Gray show {loc. cit., fig. 9) a whorl of polyps seen from the 

 side, and (fig. 8) a piece of the stem with a row of six whorls. Although many details 

 are left um'epresented in the figure, yet the species may be recognised thereby. The 

 description of the species, as is usual with Gray, is very short, and only in his later 

 publications was the generic diagnosis of Primnoella given. In 1876 Verrill {loc. cit.), 

 with his usual ability, gave a detailed desciiption. 



Of the several specimens which must be distinctly referred to this species as found 

 in the Challenger collection, the largest has a length of 500 mm.; the thickness of the 

 axis at its base is 2 mm. Sixteen to twenty calyces are to be found, each 2 mm. long, 

 on each closely packed whorl. Typical j^ieces come from Port Jackson, Australia, from 

 a depth of 30 to 35 fathoms. 



Near to this station, in Twofold Bay, specimens were dredged from a depth of 

 150 fathoms, which in the form of the calyces and scales appear to belong to the 

 same species, but difier with regard to the number of calyces which constitute a 

 whorl. 



