1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 641 
of the areolae, but also in the appearance of the rays and length of 
the intervals between the compartments. In Asterom. centraster , 
Johnson, the intervals between the compartments are continued 
to the centre, and their outer ends are swollen and knob-like. 
From A. brebissoniana it is readily distinguished by the straight 
instead of geniculate rays. 
Habitat. — Balearic Islands (F. Soderlund). 
A. Icevis. Grev., Trans. Micr. Soe. Lond., 1862, p. 51, pi. viii. 
fig. 33. — Diam. *0275 mm. Central rosette and areolate area 
absent. Markings : rays 6, straight ; the compartments reaching to 
about f of radius inwards, their inner ends transversely truncate, 
sometimes slightly flexuous or concave towards . the centre ; the 
areolae obscure, least evident towards the border; the intervals 
extending to about \ of distance between their inner ends and 
border, tapering gradually outwards with the inner ends convex. 
Border narrow, hyaline, indistinct. 
Habitat. — Barbados deposit (Greville !). 
A. marylandica. Ehrb., Mon. Ber. Ah., 1844, p. 76, fig. 10 
(June 1844). — Diam. '0375 to J5 mm. Central areolate area 
absent. Markings : the rays 4 to 12, straight, or but slightly arcuate, 
diverging from the centre, sometimes dichotomous or dividing into 
three equal rami ; the compartments reaching from § to J of radius 
inwards, their inner ends uniformly convex towards centre, some- 
times truncate or slightly emarginate, rarely unsymmetrical ; the 
areolae distinct, subequal on inner § of compartments, or decreasing 
more regularly outwards from 6 to 10 in *01 mm.; a band of more 
prominent submuriform areolae around their edges; the intervals 
expanding gradually outwards, their outer ends reaching close to the 
border. — Muller, Abh. Ber. Ah., 1841, p, 232, pi. vi. fig. 4 (no name); 
Bail., Amer. Jour. Sci., 1845, vol. xlviii. pi. iv. fig. B; Brightw., 
Quart. Jour. Micr. Sci., 1860, p. 94, pi. v. fig. 3; Wallich, Trans. 
Micr. Soc. Lond., 1860, p. 47, pi. ii. figs. 14, 15 ; Grev., Trans. Micr. 
Soc. Lond., 1860, p. 108, pi. iii. figs. 1-4 ; Ralfs in Pritch. Inf., p. 
836, pi. xi. fig. 33 ; Grev., Trans. Micr. Soc. Lond., 1862, p. 44, 
pi. vii. figs. 1-3 ; A. septenaria, Johnson, Amer. Jour. Sci., 
1852, ser. 2, vol. xiii. p. 33; A. impar, Shadb., Trans. Micr. Soc. 
vol. xvi. 7/11/89 2 s 
