A 'Revision of the Genus Aulacodiscus Ehrb. By J. Rattray. 375 



rows diverging slightly at outer ends. Border striae delicate, 14 in 

 - 01 mm. Processes 4, insertion 1/4 to 3/11 of radius from circum- 

 ference, clear space at base absent. — PL V. fig. 4. 



The scar of the broken-oflf process is elongately elliptical. 



Habitat : Sysran deposit, Eussia (Kitton !). 



A. prominens Kitton MS. — Diam. 0'0875 mm. Surface with 

 central area much elevated, quadrate, angles extending to processes, 

 outer edges with a slight concavity about middle of compartments ; 

 slope to border steep. Colour bluish at centre, elsewhere smoky grey. 

 Central space rounded, about 1/35 of diam. broad, clear. Markings 

 5 to 6 in 0*01 mm., rows slightly deflected at processes, secondary 

 oblique rows indistinct. Primary rays manifest, cruciform, rows 

 diverging slightly in outer 1/3 of length. Border striae 8 in • 01 mm., 

 about 1/23 of radius broad, inner edge indistinct. Processes 4, 

 insertion about 6/17 of radius from circumference, hourglass-shaped, 

 constriction median, wide, free ends protuberant, clear space at base 

 small.— PI. V. fig. 5. 



Habitat : Sysran deposit, Eussia (Kitton !). 



A. Kittoni Amott, in Pritch. Inf., p. 844, pi. viii. fig. 24. — 

 Diam. 0-0625 to 0*23 mm. Surface flat for about 1/3 of radius, 

 with outer edge faint and concave between primary rays, the rays 

 often rising somewhat to processes, slope to border gentle. Colour 

 pale brownish or smoky grey, rarely clear throughout. Centre with 

 distinct rosette, 1/12 to 1/23 of diam. broad, rarely inconspicuous. 

 Markings 4^ to 5 in 0- 01 mm., without interspaces, rows straight or 

 slightly sigmoid with sharper curve towards periphery, secondary 

 oblique rows distinct. Primary rays well marked, sometimes inter- 

 rupted towards centre. Border striae 4 to 5 in 0' 01 mm., 1/24 to 

 1/40 of radius broad. Processes 4 to 8, rarely 3, 2, 1, or ; insertion 

 about 1/6 of radius from circumference; a long, straight, tapering 

 mark opposite primary rays, with two transverse or oblique rounded 

 lobes at its outer end and a broad crescentic band on peripheral side ; 

 in girdle aspect mammiform, with a clear apical portion protruding at 

 sides and on peripheral but not on central aspect. Girdle ' 025 mm. 

 wide on valve 0*13 mm. in diam., with faint parallel lines. — Sch. Atl., 

 pi. xxxvi. figs. 5-7 ; pi. xli. fig. 6. A. Isevis Brightw., Quart. Journ. 

 Mic. Soc, 1860, p. 95, pi. vi. fig. 13. A. Ehrenbergii Janisch., 

 Abh. Sch. Ges. vater. Cult., 1861, p. 162, pi. ii. fig. 6 ; Sch. Atl., 

 pi. xxxvi. figs. 3, 4. A. BrightweUii Janisch, ibid., 1861, p. 162, 

 pi. ii. fig. 7 ; Sch. Atl., pi. xxxvi. figs. 8, 9. A. deformis (Habirsh. 

 Cat. Diat. § AuIacocUseus) is, according to Habirshaw, equivalent to 

 Eupodiscus deformis, and is a var. of A. Kittoni. 



Habitat : Peruvian guano (Greville ! Weissflog ! Eae ! Hardman ! 

 Harrison) ; Monterey stone (Gregory, Kitton, Ball's, Cleve !) Sta. 

 Monica deposit (Eae ! Kinker !) ; Islay, Peru (Kitton, Hardman !) ; 

 " New Zealand " (Johnson !) ; Bay of Islands, New Zealand (Hard- 

 man !) ; San Francisco (Witt) ; sea foam, Sta. Cruz, California (H. L. 

 Smith, Weissflog !) ; marine algae, California (Eae !) ; Monterey sea- 



