1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 467 
•0275 mm. Surface slightly convex. Central space and rosette 
absent. Markings hexagonal, central dots sometimes evident, 
decreasing but slightly from the centre outwards, about 2i in 
*01 mm. Border narrow, showing evident short radial lines. 
Habitat. — Simbirsk (Schmidt). 
V ar. tenuior , nov. C. subconcavus , G run. , var.? Sch. , Ai?.,pl. lix. fig. 
15. — Diam. *038 mm. Markings smaller, decreasing more distinctly 
outwards, towards the centre 3, towards the border 4 in ’01 mm.; a 
single band of smaller areolae adjacent to the border. Border 
smooth, narrow. 
Habitat. — Simbirsk (Schmidt). 
C. vigilans. Sch., Atl ., pi. cxiv. figs. 11, 12. — Diam. *0455 to 
•068 mm. Surface slightly convex. Central space and rosette 
absent. Markings round, robust, pearly, smooth, largest at the 
centre, decreasing rapidly near the border ; at the centre 2, at the 
border 4 in ’01 mm.; central papillae faint, interspaces hyaline. 
Border sharply defined, formed by one or two bands of rounded 
granules in contact laterally, and 6 or 7 in *01 mm. 
Distinguished from C. subvelatus by the larger size and by the 
form of the markings and the distinct character of the border. 
Habitat. — Archanjelsk-Kurojedowo (Schmidt). 
C. Molleri. Sch., Atl., pi. lix. fig. 17. — Diam. *0625 to -08 mm. 
Surface convex, and more opaque at the centre. Central space and 
rosette absent. Markings hexagonal, decreasing regularly but some- 
what rapidly from the centre outwards, at the centre most distinct 
2 to 2J, towards the border more faint, 3 in *01 mm.; at the border a 
single band of quadrate equal areolae with longer axis at right angles 
to the radius, 3 in *01 mm.; oblique decussating rows obvious, 
straight or slightly concave towards the border. Border narrow, 
hyaline. 
Habitat. — Mors deposit (Schmidt, Cleve! Grunow, Moller !).* 
Yar. macroporus. Grun., Denk. Wien. Ak., 1884, p. 84, 
pi. iv. (D), fig. 25. — Diam. *063 to *125 mm. Markings at the 
centre 2, at the border 4 in *01 mm., their surface obsoletely 
* In the collections of Julien Deby and of Prof. Cleve. 
