634 
Proceedings of Royal Society of Edinburgh. [sess. 
Asterolampra , Grev., pro parte , Trans. Micr. Soc. Lond ., 1860, 
p. 162; Or aspedodiscus, pro parte, Brightw., Quart. Jour. Micr. 
Sci., 1860, p. 95. 
§ 1. Margin at®. 
A large central areolate area. Rays many, short, confined to a 
submarginal zone. Compartments minute. 
A. marginata. Grev., Trans. Micr. Soc. Lond., 1862, p. 50, 
pi. viii. fig. 30. — Diam. *0625 to *1125 mm. Central area 
extending outwards for § to ~ of radius, its outer edge sinuate, 
subregular ; a rosette distinct. Markings on central area areolate, 
the areolae decreasing slightly from the rosette outwards from 
4 to 5 in - 01 mm.; rows radial, straight, non-fasciculate ; secondary 
oblique decussating rows faintly marked ; rays short, straight, 
radiating from the distal angles of the sinuations about 4 of radius 
long; the compartments restricted to a narrow (about *0025 mm. 
broad) zone adjacent to the border, their inner ends convex towards 
the centre ; the intervals represented by shallow indentations. — 
Eulenst., Diat. Spec. Typ., No. 16; Craspedodiscus marginatus, 
Brightw., Quart. Jour. Micr. Sci., 1860, p. 95, pi. v. fig. 7 ; Ralfs 
in Pritch. Inf, p. 832 ; A. marginata, var. minor, Walker and 
Chase, New and Rare Diat., ii. p. 7, pi. v. fig. 8. 
This species forms the connecting link between Coscinodiscus , 
Brightwellia, and Asterolampra. In the first named genus it ap- 
proaches C. bultiens, the markings on its central area also recall those 
of C. concinnus, var. jonesiana. The interspaces between the rays 
are larger, more peripherally placed, and less sharply defined than 
in any Brightivellia, whilst its regularly areolate central portion is 
homologous to the irregular inconstant areolate areas of Astero- 
lampra decora , A. affnis, A vulgaris, & c. 
Habitat . — Barbados deposit (Johnson ! Greville ! Grove ! Eulen- 
stein !) ; Springfield deposit, Barbados (Walker and Chase) ; 
Cambridge deposit, Barbados (Deby !) ; Chalky Cliff, Barbados 
(Deby !). 
§ 2. Ductiles. 
A central areolate area. Compartments conical in outline with 
distant subradial branching, but evident lines. 
