344 Transactions of the Society. 



1/12 to 1/16 of radius broad, well marked. Processes 3 or 4, 

 insertion 1/3 to 1/G of radius from circumference, minute, constriction 

 shallow, a faint ovate oblique mark towards same side of base of each, 

 clear area at base irregularly semicircular or triangular, its edge 

 delicately striated at right angles to its margin. — A. notatus Grove & 

 Sturt, Journ. Quek. Mic. 01., 1887, pp. 9, 146, pi. iii. fig. 11. 



Habitat : Newcastle deposit, Barbadoes (Kae ! Firth !) ; Oamaru 

 deposit, New Zealand (Grove & Sturt !). 



§ 3. Badiati. 



Surface crateriform or almost flat at centre, highest zone distinct, 

 often convex and angular at primary rays, which are usually elevated. 

 Clear space at base of processes minute. 



A. hilkeUyanus Grev., Trans. Mic. Soc. Lond., 1863, p. 70, pi. iv. 

 fig. 14. — Diam. 0*075 to - 1025 mm. Surface rising for almost 1/3, 

 or flat for 5/9, of radius, outside of highest zone plain or slightly sig- 

 moid — first concave then convex between processes; no inflations; 

 slope to border gentle. Colour pale grey, darker at border. Central 

 space rounded, 1/17 to l/'20 of diam. broad, hyaline, boundary faint. 

 Markings round, 4 in 0"01 mm, decreasing uniformly to border, out- 

 lines faint, central dot distinct, interspaces minute, hyaline, rows 

 straight, radial, the shorter attenuating inwards. Primary rays incon- 

 spicuous, rows in contact or with a narrow interspace not expanding 

 outwards. Border striae 12 to 14 in 0*01 mm., about 1/40 of radius 

 broad, inner edge distinct. Processes 3 or 4, insertion 1/4 to 1/5 of 

 radius from circumference, hourglass-shaped, proximal and distal por- 

 tions equal, constrictions deep, length about 2^ times breadth, clear 

 space at base distinct. 



Habitat : Cambridge deposit, Barbadoes (Greville ! Johnson ! 

 Hardman !). 



Var. minor. — Diam. ■ 0525 mm. Surface forming a low cone, 

 convex from centre to about 1/3 of radius. Central space angular, 

 about 1/21 of diam. broad. Markings subequal, 8 in - 01 mm., rows 

 separated by narrow clear lines. Primary rays more distinct, traceable 

 to central space. Striated border absent. Processes ? insertion about 

 2/7 of radius from circumference. 



Dr. Greville had distinguished this as a species, but on what 

 appears to me insufficient grounds. The scar of the broken-off process 

 is elliptical. 



Habitat : Bridgewater, Barbadoes (Johnson !). 



Var. sparsa. A. sparsus Grev., Trans. Mic. Soc. Lond., 1866, p. 123, 

 pi. xi. fig. 6. — Diam. ' 075 mm. Surface most elevated at centre, 

 slightly convex to processes, slope to border steep. Central space 

 bluntly and irregularly 4- angled, about 1/20 of diam. broad. Markings 

 sometimes polygonal and in contact, decreasing but slightly towards 

 border, and little more crowded here than on other parts of valve. 

 Primary rays only recognized on central half when traced inwards 



