1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 639* 
subareolate ; intervals narrow, unequal, sometimes expanding 
slightly at their outer ends. Border narrow, its inner edge with 
minute irregularities, hyaline. 
This species is sometimes confounded with A. punctata, from 
which it differs in the appearance of its central space and the 
sculpturing of its compartments. 
Habitat. — Barbados deposit (Greville !) ; Springfield deposit, 
Barbados (Hardman !).* 
A. cemulans. Grev., Trans. Micr. Soc. Lond ., 1862, p. 52, 
pi. viii. figs. 34, 35. — Diam. '05 to *075 mm. Colour pale 
brownish-grey at centre and along the rays, elsewhere pale smoky 
grey. Central portion distinct, extending outwards for J to T %- of 
radius. Markings on central portion areolate, the areolse 3J to 4 
in ‘01 mm.; rays straight or but slightly arcuate; the compart- 
ments reaching from f to of radius inwards, their inner ends 
convex, with short distinct radial lines about 4 in '01 mm., and 
extending outwards for i to J of their length, their outer portion 
with delicate areolae decreasing rapidly outwards from 5 or 5J to 8 
in - 01 mm.; the intervals of equal breadth, their outer ends rounded, 
not reaching the border. Border distinct, hyaline. 
Both of the typical specimens in Greville’s collection show a dis- 
tinctly areolate central portion, and there is no indication of its 
ever being solid, as stated by Greville. In neither are the markings 
on the compartments isolated puncta. 
Habitat. — Barbados deposit (Greville !). 
§ 5. Eximi^. 
Central areolate area sometimes present. Rays rarely unequal, 
and meeting at an excentric point or absent. Compartments 
areolate, their inner ends convex, concave, or obliquely truncate 
towards the centre, sometimes bounded by a prominent areolate 
fringe; intervals rarely obsolete or occluded at their inner ends, 
reaching the border. 
A. nicobarica , Grun. Van Heurck, Syn. Diat. Belg., pi. cxxvii. 
fig. 7. — Diam. *055 mm. Central space angular, about ’01 mm. 
In the collection of Mr Julien Dely. 
