918 Transactions of the Society. 



F. larbadensis Grev., Trans. W\c. Soc. Loncl, 18G3, p. 68, pi. iv. 



fig. 8. 



Diam. 0"0875 mm. The semicircular hyaline areas about 

 • 005 mm. broad. Colour darker towards the centre. Central .space 

 0125 mm. long. Markings in the converging rows subequal, 4 in 

 O'Ol mm., elsewhere decreasing gradually for about 3/5 of radius, 

 and then more suddenly to the border. Border narrow, with minute, 

 irregularly placed, distant apicuh. 



Habitat : Cambridge deposit, Barbadoes (Johnson !). 



CRASPEDOPORUS Grev. 

 Craspedo'porus Grev. emend., Trans. Mic. Soc. Lond., 1863, p. 68. 



Valves circular, sometimes dissimilar. Surface usually with dis- 

 tinct compartments, sul >plain or the compartments sometimes rising 

 towards the border. Colour pale grey. Central space distinct, 

 rounded, sometimes small or absent. Markings punctate, areolate or 

 grjinular, without order or in radial or oblique rows, secondary sub- 

 concentric rows rarely visible, sometimes converging around processes. 

 Border with delicate striae or hyaline. Processes 5 to 11, placed on 

 the alternate compartments, subcircular, or roundly elliptical, with 

 major axis radial or at right angles to the radius, sometimes with the 

 outer edge elevated and pocket-like, a surrounding hyaline space 

 sometimes present. 



In its general characters this genus hardly approaches Coscino- 

 cliscus as stated by Greville. It is much nearer the Eupodiscem in 

 the character of the processes, but is quite distinct in other respects. 

 Some frustules with dissimilar valves have one of the valves approach- 

 ing Porodiseus. 



C. ralfsianus Grev., Trans. Mic. Soc, Lond., 1863, p. 68, pi. iv. fig. 9. 



Diam. 0"105 mm. Surface with distinct compartments, those 

 bearing the processes expanding outwards at first regularly, then more 

 suddenly near the processes, the others wider. Central area circular, 

 about 1/-4 of diam. broad, somewhat more dense than outer portion. 

 JMarkings irregularly areolate, the meshes smallest about outer edge 

 of central area, about 4 in O^Ol mm. Processes 8 to 9, subcircular, 

 with major axis radial, their distal edge sometimes elevated, giving 

 a pocket-like appearance. 



Habitat : Cambridge deposit, Barbadoes (Ealfs, Johnson). 



C. johnsonianus Grev., Trans. Mic. Soc. Lond., 1863, p. 69, pi. iv. 



fig. 10. 



Diam. • 625 to • 07 mm. Surface compartments with straight 

 elges, those bearing the processes rising gradually outwards, the 

 others fiat. Central space pentagonal, hyaline, about 1/5 of diam. 



