1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 583 
irregular, but beyond the semiradius in distinct, somewhat bent, 
subradial n on-fasciculate rows. Border narrow ; striae 6 to 8 in 
*01 mm. distinct. — (PI. II. fig. 1.) 
Habitat. — Galapagos Islands (Weissflog !). 
C. tabularis, Grun., Denk. Wien. Ak., 1884, p. 86. — Diam. 
•0605 mm. Central space subcircular, distinct, about i of diam. 
broad, bearing a few isolated round granules. Markings round, 
granular, subequal or somewhat smaller near the border, about 6 in 
•01 mm. interspaces hyaline; a narrow clear band about Jg-of radius 
broad adjacent to the border; at its outer edge distinct apiculi at 
intervals of about *01 mm. Border narrow, hyaline. — Sp. n. ? 
Sell., Atl.y pi. Ivii. fig. 43. 
Habitat. — Table Bay (Schmidt). 
C. Thumii. Cleve, Jour. Quek. Micr. Cl., 1885, p. 175, pi. xiii. 
fig. 17. — Obtusely triangular, or with a unilateral compression, or 
circular. Diam. *075 to '125 mm. Central space subcircular, 
about J of diam. broad, hyaline, with diverticula extending out- 
wards between the longer rows of markings. Markings small, 
rounded, granular, 6 in - 01 mm., subequal to but most crowded 
around the border; the rows straight, with wide hyaline inter- 
spaces towards the centre. — Sch., Atl., pi. cxiv. fig. 10. 
Specimens with two central spaces, separated by a single row of 
markings, sometimes occur. 
Habitat. — Briinn Tegel (Weissflog !) ; Mahren deposit (Deby !). 
C. comptus. Cstr., Diat. Cliall. Exped., p. 157, pi. xiii. 
fig. 9. — Diam. *1 25 mm. Central space circular, hyaline, about Jg- 
of diam. broad, without a distinct limiting band of markings. 
Markings punctiform ; rows radial, only a few reaching the central 
space, the majority terminating about f of radius from the centre, 
on the other -J of radius crowded, interspaces hyaline. Border 
distinct, narrow, hyaline. 
Distinguished from C. Thumii by the smaller markings, fewer of 
which pass to the central space, and by their more crowded arrange- 
ment on the outer -f of the radius. The relationship to C. dimorphus, 
noted by Castracane, is remote. 
Habitat.— Antarctic Ocean, H.M.S. Challenger (Castracane). 
