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



The scales are relatively large. The upper row oif calyx scales is higher than broad, 

 with strong prominences, and a median keel which runs out into a siort spine. Height 

 to breadth, 0'54-0"42 mm. ; the succeeding scales are broader than high, with small 

 teeth on the upper edge, often interspersed with stronger teeth. Height to breadth, 

 0-42-0-5 mm. 



The opercular scales are triangular, pointed, with median keel. Height to length, 

 0'5-0"3; 0"65-0'4 ; 0'43-0'2 mm. The scales of the ccenenchyma are irregularly triangular 

 to four-cornered with unequal sides. Height to breadth, 0"46-0'35 ; 0'46-0'2 ; 0"3- 

 0-25 mm. 



Several specimens which were obtained by the Challenger may be referred to this 

 species. 



The generally simple stem rises from a flat, leaf-like, calcareous base, which covers 

 stones, &c. 



The axis is horny, calcareous, brittle, yellow, with a golden sheen on the surface. Its 

 transverse section is oval and the whole stem is twisted in a long spiral. The length of 

 the stem reaches 150 to 200 mm.; the thickness at the base 2 to 2'5 mm. The twigs, 

 which arise from three sides of the stem in an ascending spiral, are generally simple, up to 

 25 mm. long, coming off from the stem at nearly right angles. Their axis is stiff and 

 bristle-like. The club-shaped polyps have a length of 2 mm. There are seven trans- 

 verse rows of scales present and eight longitudinal rows. The form and size of the scales 

 agree completely with those of the type specimen. 



Calyx scales. — Upper row with short spines. Height to breadth, 0"6-0'29 ; 0"61- 

 0'3 ; ()"46-0'3 mm.; those of the following rows are broader than high, 0'37-0'75; 0"37- 

 0-58; 0-3-0-4 mm. Scales of the ccenenchyma, 0-35-0-3 ; 0-4-0-26 ; 0-45-0-35 ; 

 0-25-0-2 mm. 



Habitat. — Station 148a, off the Crozets ; depth, 550 fathoms; bottom, hard ground, 

 gravel, shells. 



5. Thouarella affinis, n. sp. (PI. XXI. fig. 3). 



Very like the preceding species. From the simple stem, which appears twisted in 

 a long spiral, simple twigs come off, in ascending spirals, from three sides. These bear 

 the polyps. The polyp calyces are 2 mm. long and contain scales, which are distinct 

 from those of the preceding species in size and sculpture. The scales of the last row 

 are not provided with spines but are simply toothed. The scales of the calyx are less 

 prominent. 



The specimen, broken into three pieces, has, from the l)ase to the apex, which 

 contains the summit of the colony, a length of 220 mm. The main stem, from which 

 twigs come off along its whole course, has at the lower end a diameter of 2 mm. and 



