A Revision of the Genus Aulacodiscus Ehrb. By J. Rattray. 345 



from processes. Border striae 8 to 10 in 0*01 mm., about 1/20 of 

 radius broad. Processes 3 or 4, insertion about 1/5 of radius from 

 circumference, cylindrical, attenuating towards base, free ends 

 emarginate. 



Habitat: Barbadoes deposit (Greville !). 



The Ceylon specimen from Witt, figured by Schmidt (Atl. pi. cii. 

 fig. 3), appears to me to be nearer to var. sjparsa from its markings, 

 primary rays, and processes, but its surface is very convex. 



A. decorus Grev., Trans. Mic. Soc. Lond., 1864, p. 82, pi. x. fig. 2. 

 — Diam. ■ 1025 to • 13 mm. Surface flat to about semi-radius, or 

 slightly depressed at central space, with outer edge distinct and con- 

 cave, outermost 1/3 of compartments almost flat. Colour pale bluish 

 at centre, elsewhere grey, darker towards border. Central space 

 irregularly rounded, 1/20 to 1/21 of diam. broad, hyaline. Markings 

 angular, 5£ to 6 in 0'01 mm., outlines faint, near processes oval, 

 oblique, rows subradial, converging round processes, concentric near 

 centre, interspaces most evident at origin of shorter rows. Primary 

 rays with rows diverging slightly outwards. Border strife 12 to 14 

 in - 01 mm., about 1/27 of radius broad, inner edge sharp. Pro- 

 cesses 6, insertion about 1/5 of radius from circumference, proximal 

 portion rounded, distal subcylindrical, free ends truncate, length 1^ 

 to 2 times breadth. — Sch. Atl., pi. cv. fig. 8. 



The scar of the broken- off process is oval. 



This species is sometimes confounded with A. amoenus, but bears 

 to it but little affinity. A. Stoschii, figured by Walker and Chase, is 

 distinct. A Panama specimen in the Koyal Botanical Museum, Stock- 

 holm, named by Cleve A. Stoschii, is A. angalatus var. neogradensis, 

 and Weissflog's ' Gazelle ' specimen, also named A. Stoschii, is 

 A. amoenus var. hungarica with 5 processes. 



Habitat : Cambridge deposit, Barbadoes (Greville !). 



Var. Stoschii. A. Stoschii Janisch in Sch. Atl., pi. xxxiv. fig. 11. 

 — Diam. 0*165 to 0' 175 mm. Central portion flattened to about 

 5/7 of radius, outer edge more distinct, convex on compartments ; 

 inflations short, abrupt; slope to border gentle. Markings 5 in 

 O'Ol mm., concentric rows less distinct. Primary rays indistinct 

 towards centre. Processes 6, cylindrical, insertion about 1/6 of radius 

 from circumference. 



Habitat : Cambridge deposit, Barbadoes (Greville ! Johnson !) ; 

 ' Gazelle ' Exped. (Janisch). 



Var. canariensis. — Diam. ' 14 mm. Central portion flat to 3/7, 

 rarely to 2/3 of radius ; inflations more distinct, rarely short. Central 

 space larger (1/9 to 1/14 of diam.), sometimes with short extensions 

 into apices of compartments. Markings 4 in 0'01 mm., without 

 interspaces, secondary fringe-like rows around processes more evident. 

 Border striae coarse, 8 to 10 in 0*01 mm. Processes 7, free ends 

 rounded, constriction median. — PI. VI. fig. 6. 



Norman proposed to erect a new species for these valves ; Hardman 

 has regarded them as a Yar. of A. angirfatus. 



