1888-89.] Mr John Rattray on the Genus Coscinodiscus. 667 
— unpublished). Diam. ’07 
mm. 
Rays 1 4, zig-zag. 
Areolae 
small. 
A. Cohnii. Janisch {ibid., 
1860, 
p. 160, pi. ii. b. 
fig. 26- 
unpublished). Diam. *0805 
mm. 
Rays 15, zig-zag. 
Areolae 
small. A. cleveanus , Janisch, is erroneously mentioned in Habir- 
shaw’s Cat. Diat ., § Aster omphalus, as found in Abh. Schl. Ges. 
vater. Cult, 1860, p. 160, pi. ii. b. fig. 26. The name given in the 
paper quoted being A. Cohnii. 
A. Ehrenbergii. Janisch. {ibid., 1861, p. 161, pi. ii. b. fig. 27 — 
unpublished). Almost circular. Diam. *095 mm. Rays 16, zig- 
zag-shaped. Areolae small. 
A. Braunii. Janisch. {ibid., 1861, p. 161, pi. ii. b. fig. 28 — 
unpublished). Diam. T05 mm. Rays 17, zig-zag. Areolae small. 
Artificial Key. 
f Outline flabelliform to subtriangular, oval or 
elliptical, ........ 2. 
1. -{ Outline circular or subcircular, .... 3. 
| Outline subregularly oblong, with sides slightly con- 
L concave at their middle, ..... sarcophagus. 
I 
f Compartments longest adjacent to snbobsolete 
interval, decreasing away from this ; rays simple ; 
areolse obscure, 
l 
Compartments shortest at ends of minor axis ; rays 
sometimes dichotomous ; the areolse delicate, 12 to 
14 in '01 mm., ....... 
flabellatus. 
cleveanus. 
3. 
f Rays simple, 
\ Rays sharply bigeniculate, 
4. 
5. 
f Intervals between compartments prolonged to centre ; 
^ I outer ends of rays knob-like, penetrating a short 
* ] distance into compartments, ..... 
USTo such structure, . . . 
centraster. 
6 . 
f Inner ends of compartments concave towards centre ; 
centro-lateral area acutely Y-shaped; subobsolete 
interval rapidly attenuating outwards, . . . wallichianus. 
Inner ends of compartments obliquely truncate on 
each side of the rays ; centro-lateral area sometimes 
! with inner ends obtuse, ..... variabilis. 
’ } Inner ends of compartments rounded, ... 7. 
I Inner ends of compartments more conical, . . 8. 
| Inner ends of compartments concave towards centre ; 
centro-lateral ared with sides concave outwards ; 
| one ray opposite this area more robust than the 
l others ; intervals expanding outwards, . . . nankoorensis. 
7 . 
f Structure markedly excentric ; central area opposite 
I subobsolete interval, maleiform, extending across 
] the hyaline portion of valve, 
I Structure not markedly excentric, .... 
arachne. 
9. 
