584 Proceedings of Royal Society of Edinburgh. [sess. 
C. confertus, sp. n. Sell., Atl. , pi. Iviii. fig 22 (no name). — 
Diam. about ’04 mm. Central space and rosette absent. Markings 
punctiform, interspaces large, unequal, but markings not crowded 
either towards centre or border ; rows faint. Border indistinctly 
defined; striae 6 in *01 mm. 
Distinguished from C. marginulatus var. sparsa , Grun., from 
Campeachy Bay, by the radial arrangement of the markings and the 
less prominent border. 
Habitat. — Cape of Good Hope (Schmidt). 
C. polygonus. Cstr., Diat. Cliall. Exped ., p. 161, pi. xxii. fig. 
6. — Polygonal. Diam. about *1 mm. Central space subcircular, 
about of diam. broad, bearing a few isolated granules. Mark- 
ings punctiform, interspaces hyaline, unequal, largest opposite the 
origin of the shorter rows ; rows often interrupted ; a narrow 
hyaline band adjacent to the border. 
The polygonal outline of the valve is probably the result of 
fracture. This species is close to C. Thumii , but is distinguished 
by the absence of crowding in the arrangement of the markings 
towards the border, and by the hyaline zone adjacent to the latter. 
Habitat. — Antarctic Ocean, H.M.S. Challenger (Castracane). 
C. elongatns , Grun. Yan Heurck, Syn. Diat. Belg ., pi. exxv. 
fig. 14. — Elongately elliptical. Major axis '083 mm., about 54 
times minor. Central space absent. Markings punctiform, ir- 
regular on a small central area ; rows straight along the minor 
axis, elsewhere convex towards the extremities of the major axis 
and radial, most crowded on a narrow band around the border. A 
single interrupted row running along the major axis; apiculi 2, 
minute, one at each end of the major axis ; interspaces hyaline. 
The valve figured by Yan Heurck (ibid., pi. exxv. fig. 15) is 
similar, but possesses an evident pseudonodule, and so belongs to 
Actinocyclus. 
Habitat. — Mejillones guano (Yan Heurck). 
C. pauper. Tru. and Witt, Jeremie Diat., 1888, p. 13, pi. ii. 
fig. 11. — Diam. -06 mm. Surface flat. Central space circular, 
j-L of diam. broad. Markings round or obtusely angular, subpearly; 
towards the centre 3J, towards the border 4J, in ’01 mm. ; smaller 
