A Revision of the Genus Aulacodiscus Ehrb. By J. Rattray. 357 



meshes just visible, secondary oblique rows conspicuous at outer ends 

 of inflations. Border indistinctly denned, striae 10 in O'Ol mm., 

 about 1/20 of radius broad. Processes 7, insertion 1/8 of radius from 

 circumference, cylindrical, or tapering somewhat towards outer ends, 

 small, free ends emarginate. — PI. V. fig. 2. 



The scar of the broken-off process is oval. 



Habitat : Cambridge deposit, Barbadoes (Johnson !). 



A. anthoicles Sch., Atl., pi. ciii. fig. 1. — Diam. - 1125 mm. 

 Surface rising gently for about 1/5 of radius to highest zone, the 

 latter about 2/5 of radius broad ; slope near border gentle, outer ends 

 of inflations sharply defined by a curved dark line. Colour pale grey, 

 darker towards border. Central space pentagonal, sides inwardly 

 convex, 1/15 of diam. broad, sometimes rounded. Markings rounded, 

 6 in • 01 mm., smaller near central space, rows on peripheral region 

 in fasciculi, separated by wide irregular interspaces, more hyaline than 

 those between the component rows of the fasciculi. Primary rays with 

 rows diverging from inner ends, outside highest zone interspace much 

 wider. Border striae 10 to 12 in " 01 mm., about 1 /23 of radius broad. 

 Processes 5, insertion 1/3 to 2/7 of radius from circumference, proximal 

 part rounded, distal subcylindrical, free ends truncate, length about 

 three times breadth. — The scar of the broken-off process is oval. 



Habitat : Barbadoes (Weissflog !). 



§ 7. Spectati. 



Surface flat or slightly depressed at centre, highest zone angular 

 at processes, edges concave outwards on compartments, slope to border 

 steep, sometimes gentle ; inflations as low mammillations beneath 

 processes. Central space punctate, granulate or hyaline. 



A. polygonus * Grun., Pant. Fossil. Bacil. Ung., p. 59, pi. xxvi. 

 fig. 236. Valve polygonal, margin of compartments slightly con- 

 cave. Diam. 0*182 to 0'35 (?) mm. Surface flattened from centre 

 almost to processes, concavities between the latter shallow. Colour 

 pale grey, darker at border. Central space inconspicuous, 1/16 to 

 1/18 of diam., broad. Markings round, outlines delicate, 3 to 4^ in 

 O'Ol mm., rows radial, straight. Primary rays indistinct. Border 

 with coarse striae, 6 to 8 in - 01 mm. Processes 10 to 12, insertion 

 1/15 to 1/23 of radius from circumference, conical, free ends truncate, 

 no clear space at base, length 2j times breadth. — A. polygonus var. 

 tfolygibha Grun., Pant., ibid., pi. xxvi. fig. 237. 



Habitat : Szent Peter deposit (Grunow) ; Oamaru deposit 

 (Pantocsek !). 



A. amoenus Grev., Trans. Mic. Soc. Lond., 1864, p. 10, pi. i. 

 fig. 3. Diam. 0-07 to 0'28 mm. Surface with highest zone 1/4 to 

 1/8 of radius broad, outer edge distinct, straight or concave between 

 processes; inflations abrupt on peripheral side. Colour pale grey, 



* Of this species only Pantocsek's fragmentary Oamaru specimen has been ex- 

 amined. 



