646 Proceedings of Royal Society of Edinburgh. [sess. 
A. eximia. Grev., Trans . Micr. Soc. Lond ., 1865, p. 99, pi. viii. 
fig. 10. — Diam. ’0875 to *15 mm. Central rosette distinct, a 
central areolate area about *036 mm. broad. Markings : on central 
area unequal areolse 2 to 2J in *01 mm.; rays 22, straight ; the 
compartments reaching about f of radius inwards, their inner ends 
convex, bounded by a single band of large areolae about 3 in 
•01 mm., and gradually decreasing in length from the radii out- 
wards, elsewhere the areolae quadrate, decreasing gradually from 
3 to 4 in *01 mm.; intervals of equal breadth throughout, their outer 
ends convex, reaching close to the border. 
Habitat. — Cambridge deposit, Barbados (Hardman) ; Chalky 
Cliff, Barbados (Deby !). 
A. concinna. Grev., Trans. Micr. Soc. Lond., 1862, p. 46, 
pi. vii. figs. 10-12. — Diam. *075 to *1 mm. Central areolate area 
absent. Markings : rays straight, springing from centre ; the 
compartments reaching from -J- to \ of radius inwards, their inner 
ends transversely truncate or slightly convex, bounded by a single 
band of large areolse 4 in ‘01 mm. at their inner ends, sometimes a 
single large areola at each of the centro-lateral angles of the 
compartments ; elsewhere the markings 6, decreasing gradually out- 
wards to 8 in *01 mm.; the intervals expanding slightly outwards, 
their outer ends convex, reaching close to the border. 
Habitat. — Barbados deposit (Greville !). 
A. vulgaris. Grev., Trans. Micr. Soc. Lond., 1862, p. 47, pi. vii. 
figs. 17-20. — Diam. ‘0375 to ‘055 mm. A central areolate area 
sometimes present. Markings on central area unequal, about 4 in 
*01 mm., rarely a single round areola only present; rays straight; 
the compartments reaching from ^ to J of radius inwards, their 
inner ends concave at the middle, bounded by a distinct band of 
large areolse about 4 in *01 mm., those at the centro-lateral angles 
largest, and protruding into the interradial spaces with their 
central ends rounded, sometimes those of the adjacent compartments 
expanding towards one another at their inner ends so as almost to 
exclude the intervals; elsewhere the areolse 8 to 10 in ’01 mm.; 
the intervals expanding for some distance outwards, their outer 
ends sometimes reaching close to the border, convex outwards. — 
