1888-89.] Mr John Rattray on the Genus Coscinodiscus. 535 
Habitat. — Antarctic Ocean, Patagonia (Cleve and Moller !) ; Table 
Bay (Cleve !). 
C. mirificus. Cstr., Diat. Chall. Exped., p. 154, pi. iii. figs. 6, 
6a. — Diam. ’326 mm. Central space irregularly subcircular, about 
j! t of diam. broad. Markings hexagonal, their sides composed of 
closely placed round granules, the central dots distinct, decreasing 
but slightly to the border ; towards the centre 6, at the border 8, in 
*01 mm. Border formed by a simple line. 
In its large central space, this species approaches C. asteromphalus 
var. pabellanica , Grun., but is distinguished by the absence of a 
distinct band around the central space, and by the greater uniformity 
of the markings. 
Habitat . — Hong Kong, in the sea, H.M.S. Challenger (Castra- 
cane). 
C. Hauckii , Grun. Van Heurck., Syn. Diat. Belg ., pi. xciv. 
fig. 29. — Diam. '0365 mm. Central space absent. Markings 
obscure, punctiform, irregular, and with hyaline interspaces on the 
central portion, which extends outwards for § of radius, on outer 
J- more minute, closely disposed in crowded radial lines, 16 in 
'01 mm.; apiculi sometimes evident, inserted near border about 2 
in *01 mm. — Cleve and Moll., Diat., No. 210. 
Habitat. — Rovigno (Van Heurck, Cleve and Moller !) ; Green 
land (Cleve !) ; Labuan ? (Cleve !). 
C. liocentrum. Ehrb., Abh. Ber. Ak., 1870, p. 53, pi. ii. 2. fig. 9. 
— Diam. '075 mm. Central space extending almost to semiradius, 
smooth. Markings polygonal, delicate, increasing slightly outwards ; 
rows distinct. 
This species is at once characterised by the large size of the 
central space, in which it approaches C. mesoleius, Cleve. 
Habitat. — Humboldt Valley deposit, Cal. (Ehrenberg). 
C. vacuus , sp. n. Melosira ? Sch., Atl., pi. Iviii. fig. 29. — Diam. 
about *03 mm. Central space large, extending outwards for about 
j of radius. Markings minute, punctiform, forming closely dis- 
posed radial rows, on outer ^ of radius. Border narrow, indistinct. 
This is distinguished from C. Hauckii , Grun. (Van Heurck, Syn. 
