580 Proceedings of Royal Society of Edinburgh. [sess. 
Distinguished from C.^apollinis by the smaller size and evident 
decussate arrangement of the markings. 
Habitat. —Bain’s Farm upper stratum, Oamaru deposit (Grove !). 
C. biplicatus , Grun. Yan. Heurck, Syn. Diat. Belg ., pi. cxxxii. 
fig. 6. — Diam. *0715 mm. Surface with an elongated somewhat 
curved depression on each side of the valve at about § of radius 
from the centre. Central space angular, about of diam. broad. 
Markings punctiform, most evident about semiradius, around the 
border on a hand about J of radius broad, minute in crowded radial 
rows ; rows substraight. Border narrow, hyaline. 
Distinguished from C. 'pellucidus by the elongated depressions, 
the central space, more prominent markings, and distinct narrow 
hand adjacent to the border. 
Habitat. — Samoa Islands, Cuxhaven (Yan Heurck). 
C. bengalensis , Grun. Yan Heurck, Syn. Diat. Belg ., pi. cxxxii. 
fig. 9. — Diam. '1065 mm. Surface with a faint undulation- about 
| of radius from centre. Central space indistinct, rounded, hear- 
ing isolated granules. Markings punctiform, somewhat laxly dis- 
posed around the centre 7 to 8 in -01 mm., increasing slightly to 
about | of radius, again decreasing to the border ; secondary oblique 
decussating rows faint ; apiculi small, at intervals of about *01 mm. 
Border sharply defined ; striae delicate, regular. 
Distinguished from C. pellucidus by its somewhat more prominent 
markings, its apiculi, and striated border. 
Habitat. — Elephant Point, Bengal (Yan Heurck). 
C. pellucidus , Grun. Yan Heurck, Syn. Diat. Belg., pi. cxxxii. 
fig. 8. — Diam. *0325 to *045 mm. Surface sometimes with a faint 
undulation about the semiradius. Central space absent. Markings 
punctiform, recognised with diffiulty, least crowded towards the 
centre; interspaces clear; rows straight or substraight. Border 
hyaline. — Cleve and Moll., Diat., Ho. 172; Odontodiscus pellucidus, 
Grun., Vega Exped., Vetensh. Jakttag. Stockh., Bd. iii. 1883, 
p. 488. 
Habitat. — Davis Straits (Grunow, Cleve and M oiler !) ; Green- 
land (Cleve !) ; Maghellan Straits (Cleve !). 
