354 Transactions of the Society. 



Var. jonesiana* A. jonesianus Grev., Trans. Mic. Soc. Lond., 

 1862, p. 24, pi. ii. fig. 5.— Diarn. 0-261 rain. Surface flat to 3/10 

 of radius. Central space oblong or angular, limiting areolae larger 

 than those on compartments. Markings mostly hexagonal, rows 

 deflected at processes, rarely subfasciculate, when apices are in focus 

 elongated, opaque areas are visible opposite ends of shorter rows. 

 Processes 5 to 8, insertion 1/6 to 1/7 of radius from circumference, 

 proximal portion rounded, distal cylindrical, length 4 times breadth. 



Habitat : " Guano " (Macrae !) ; Bolivian guano (Rae !). 



A. secedens Sch. Atl., pi. cvi. fig. 2. Diam. -24 mm. Surface flat 

 to about 3/10 of radius; highest zone occupying middle third, angular 

 at processes, sides straight, abrupt ; slope to border steep. Colour pale 

 grey. Central space angular, about 1/90 of diam. broad, limiting 

 markings equal. Markings polygonal, 4 in O'Ol mm., central dot 

 inconspicuous. Primary rays distinct, the rows diverging slightly at 

 outer ends. Border striae 8 in * 01 mm., about 1/24 of radius broad, 

 inner edge distinct Processes 5, symmetrical, insertion about 1/5 

 of radius from circumference, proximal portion short, constriction 

 shallow, free ends knob-like, no clear space at base. 



Habitat : Panama shell-scrapings (Kinker !). 



A. compactus sp. n. — Diam. ■ 175 to • 2 mm. Surface, central 

 portion flat to processes, sides deeply concave outwards between these; 

 slope to border gentle. Colour highest area lurid, remainder dark grey. 

 Central space rounded, 1/18 to 1/20 of diam. broad, coarsely punctate. 

 Markings polygonal, 4 in • 01 mm., rows parallel to that at middle of 

 compartments or subradial, secondary concentric bands inconspicuous 

 towards centre. Primary rays distinct, rows diverging in outer 1/4 of 

 length. Border granules 6 to 8 in 0*01 mm. in a single band, or 

 striae 8 in • 01 mm., sometimes a narrow clear space at inner side. 

 Processes 10, insertion 1/7 to 1/8 of radius from circumference, sub- 

 cylindrical, constriction median, slight. — PL V. fig. 8. 



Habitat : Sta. Maria deposit (Kinker !) ; Newcastle deposit, Bar- 

 badoes (Firth !) 



A. patens sp. n. — Diam. " 27 mm. Surface flat from centre for 

 about 1/11 of radius, thence sloping gently to a slightly angular 

 clear zone, about 1 /28 of radius broad, and from this somewhat more 

 steeply to border, outside of the clear zone the primary rays slightly 

 elevated. Colour pale grey. Central space round, about 1/22 of diam. 

 broad, punctate. Markings polygonal and in contact, 3 in • 01 mm., 

 decreasing gradually from flat central portion to clear zone, thence 

 subequal to border, central dot brilliant, rows subradial within, more 

 nearly parallel outside of clear zone. Primary rays inconspicuous 

 within, distinct outside of clear zone, the rows diverging slightly 

 towards outer ends. Border striae coarse, 6 in 0*01 mm., about 1/55 

 of radius broad, its inner edge indistinct, separated by a narrow punctate 

 space from the markings on the compartments. Processes 13, insertion 



* Dedicated by Greville to Prof. Jones, University, Calcutta, formerly associ- 

 ated -with Dr. Macrae in the investigation of the Indian Diatomacese. 



