1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 525 
narrow hyaline areas bearing a few minute markings, attenuating 
inwards; secondary oblique rows obvious. — In H. L. Sm., Diat. 
Spec. Typ., No. 99 (no name). — (PI. III. fig. 7.) 
Habitat. — Japan (H. L. Smith !). 
C. decrescens, Grun. Sch., Atl ., pi. lxi. figs. 7 to 9, 10 ('?). — 
Diam. *038 to *05 mm. Central space and rosette absent. Mark- 
ings polygonal, with evident central papillae; at the centre 3 in 
*01 mm., decreasing rapidly on outer of radius to the border ; 
rows on the outer portion sometimes subfasciculate, secondary 
oblique sometimes outwardly curved decussating rows distinct 
towards the border. — Grun., Denk. Wien. Ak., 1884, p. 80. 
Distinguished from C. marginatus by the rapid decrease in size 
of the markings on the outer third of the valve. Sometimes 
obtusely triangular specimens occur. 
Habitat. — Springfield deposit, Barbados (Grunow) ; Dolje 
(Pantocsek) ; Barbados (Cleve !) ; west coast “Florida” U.S. Sur- 
vey (Febiger !) ; Faeroe Channel (Grove !). 
Yar. irregularis. Grun., ibid., 1884, p. 80. — Obtusely triangular, 
two of the angles more evident than the third. Diam. *068 mm. 
Markings increasing slightly from the centre to about the semi- 
radius. 
Habitat. — Springfield deposit, Barbados (Grunow). 
Var. venusta. Grun., ibid., 1884, p. 80; C. heteroporus , Ehrb., 
forma major, Grun., Sch., Atl., pi. lxi. fig. 6. — Diam. *1135 mm. 
Central space minute. Markings increasing distinctly from central 
space for about \ to f of radius, thence decreasing rapidly to the 
border; towards the centre 4, increasing to 2J in *01 mm. — C. 
argus, Grun. (non Ehrb.) in Sch., Atl., pi. cxiii. fig. 7. 
The central space and increase of the markings outwards bring 
this var. near to C. heteroporus, but the appearance of the markings 
and the arrangement around the border bring it nearer to C. 
decrescens. The transition from specimens like that shown in 
Schmidt’s Atlas, pi. cxiii. fig. 7, to C. bulliens, A. S., is easy. 
Habitat. — Springfield, Barbados (Grunow) ; iEgina (Schmidt) ; 
“ Barbados earth ” (Greville !). 
