368 Transactions of tlie Society. 



rows entire or interrupted, rarely wanting, and replaced by inner ends 

 of contiguous radial rows. Border striae 8 to 10 in 0*01 mm., 1/15 

 to 1/30 of radius broad. Processes 3, rarely 4, insertion 1/3 to 3/8 of 

 radius from circumference, oval or rounded, no clear space at base. 



Habitat : Simbirsk Polirschiefer (Weissflog !) ; Sysran deposit, 

 Siberia ( button ! Grove ! Hardman !) ; Fuur Island, Jutland (Weiss- 

 flog !). 



Var. apiculata. — Diam. 0*0875 mm. Surface flat for about 1/7 

 of radius, sides of inflations merging gradually into intervening areas 

 of compartments, basin -like depressions slight, or absent. Central 

 space round, about 1/7 of diam. broad. Markings, secondary rows 

 on compartments indistinct, apiculi prominent around processes, few. 

 Primary rays irregular, rows wider than in type. Border about 

 1/18 of radius broad, inner edge indistinct. Processes 3, oval. — 

 PI. VI. fig. 4. 



Habitat : Fuur Island, Jutland (Weissflog). 



A. acutus sp. n. — Diam. 0*195 mm. Surface with a wide but 

 shallow depression extending almost from central space to border 

 and to edges of inflations, this depression flat but slightly deepest at 

 the middle of the compartments ; inflations distinct, narrow, rising 

 gradually from the central space to the processes. Colour grey, 

 bluish at middle of compartments. Central space round, about 

 0*0125 mm. broad. Markings rounded closely disposed granules, 

 8 in 0*01 mm., in interrupted rows arranged in radial fasciculate 

 patches with wide irregular radial interspaces ; a narrow subhyaline 

 band at the zone of the processes, outside of this band coarse striae 

 8 in 0*01 mm. ; on the inflations short oblique crowded rows obvious. 

 Primary rays with the rows sometimes interrupted and widely sepa- 

 rated by a hyaline interspace expanding outwards. Border indistinct. 

 Processes 3, symmetrical, insertion about 1/8 of radius from circum- 

 ference, rounded and knob-like, clear space at their base small. 



Habitat: ? (Deby!).* 



§ 9. Oenati. 



Surface with highest zone at processes, round or angular, well 

 defined. Primary rays inconspicuous. 



A. Euttonii Grove & Sturt, Journ. Quek. Mic. CI., 1887, p. 140, 

 pl. xii. fig. 31.— Diam. * 0875 to * 21 mm. Surface flat for 9/14 to 

 10/17 of radius, highest zone 1/6 to 1/7 of radius broad. Colour grey 

 or bluish to highest zone, dark grey near border. Central space 

 angular, often irregularly quadrate, 1/16 to 1/42 of diam. broad, 

 hyaline or punctate. Markings round or angular, 3 to 3^ in 

 * 01 mm., interspaces punctate, rows radial, straight. Primary rays 

 sometimes only distinguished towards centre when traced inwards. 

 Border striae delicate, 1/17 to 1/28 of radius broad. Processes 3 to 6, 



* This rare diatom occurs in an Aulacocliscus type-plate, by Thum, in the collection 

 of Mr. Julien Deby. 



