396 Transactions of the Society. 



the mcsbes smallest close to border. Processes 4, roundly elliptical, 

 about 0-(»2 mm. broad. — Sch. Atl., pi. cviii. fig. 3. 



Habitat : Santa Monica deposit (Rae ! Gray ! Kinker ! Kitton !). 



A. suhspeciosus sp. n. 



Elliptical, major axis 0" 1125 mm., from 1} to 1.^ times minor. 

 Surface with central portion between processes somewhat elevated, 

 oval or irregularly diamond-shaped, outer edge distinct, sometimes 

 irregular, beyond this slope to border gentle. Colour pale grey. 

 Central space circular, • 015 mm. broad, distinct. I\rarkings punctate, 

 minute, in interrupted, narrow, irregular strands radiating from central 

 space, an irregular reticulum about outer edge of central portion, 

 beyond this the strife radial or oblique and curved, those converging to 

 the processes irregularly bent and irregular. Processes 2, elliptical, 

 0"015 mm. broad, the outer ends convex, high. — PI. XIV. lig. 8. 



Habitat : Santa Monica deposit (Kae ! Gray ! Deby ! Griffin !) ; 

 Los Angelos (Hardman !). 



§ 15. Species dubi.e vel EXOLusiB. 



A. (?) gigas Ehrb., IMon. Ber. Ak., 1844, p. 77.— Fragmentary, 

 sides slightly protuberant opposite process and about 90^ from this. 

 Central space absent. Markings distinct, distant, curved lines radi- 

 ating and diverging towards tumid border, the latter bearing sigmoid 

 lines separating similarly curved rows of granules. Process pro- 

 minent, convex, elliptical, around the central portion a narrow granu- 

 late band, and outside of this a broader band similar to the tumid 

 border. — Ehrb. IMikrog., pi. xix. fig. 63 ; Ralfs in Pritch. Inf., p. 84(J ; 

 Grev. Trans. Mic. Soc. Lond., 1863, p. 52. Coscinodiscus Auliscus 

 Kiitz., Sp. Alg., p. 126. 



Habitat : iEgina (Ehrenberg). 



A. ahiericanus Ehrb., MiUrog., pi. xxxiii. 14, fig. 2. — Circular. 

 Central space large irregularly quadrate, with rounded angles at pro- 

 cesses and middle of intervening area. Markings distinct, distant, lines 

 straight at right angles to line of processes, elsewhere concave 

 towards the processes. Processes 2, subcircular, their border wide. — 

 Ealfs in Pritch. Inf., p. 846 ; Grev. Trans. Mic. Soc. Lond., 1803, 

 p. 52. 



Probably, as pointed out by Ealfs, this species is the same as 

 A. sculftus W. Sm. 



Habitat: Brackish marshes near Norwich, Connecticut (Ehrenberg). 



A. ctjlindricus Ehrb., Mon. Ber. Ak., 1843, p. 271.-Of this 

 species no figure has been published. The frustule is said to be 

 cylindrical, often tibia-like, the disc on each side orbicular, plain, its 

 margin and middle portion marked by various radiating lines, the 

 apertures ( - processes) 2, oblique, large, but scarcely raised above 

 the margin. Diam. ■ 045 to • 095 mm. Specimens so named were 

 observed by Ehrenberg from Ems mud near Weimar, fiom marine 



