Greyille^ on New Diatoms. 
9 
frustular form it resembles Dhneregramma of Ralfs_, but 
differs essentially in the absence of a longitudinal median 
line or interruption of the striae in the valve. From 
Plagiogramma, Denticula, and Odontidium, it is separated by 
the absence of pervious costce^ as well as by its own peculiar 
characters. 
Terehrana Barbadensis, n. sp. Grev. (PI. II, figs. 1.2, 13). 
Hab. Barbadoes deposit, Cambridge estate; in slides 
kindly communicated by C. Johnson, Esq. 
Of this species I have met with several examples, all 
binately conjoined. The frustules are '0027'^ in length, 
sharply quadrangular, contracted below the ends, convex in 
the middle. The pores, or rather pseudo-pores, for these are 
not actual perforations, are large, circular, distinct, about 
three on each side of the serrated suture ; while the number 
of the transverse rows is about sixteen. The colour of the 
frustule is dark and smoky, and when accurately focused, 
the pores appear to transmit light, as if through a thin 
membrane. The valve is narrow, elliptical, oblong, slightly 
contracted near the extremities, which are much rounded. 
COSCINODISCUS. 
Coscinodiscus angulatus, n. sp., Grev. — Cellules equal, in 
radiating lines, about eight of which extend from the centre 
to the circumference, where each terminates in a submarginal 
tubercle ; tubercles united by a straight line of shade ; mar- 
gin rather broad, striated. Diameter '0034'^ (PI. II, fig. 11). 
Hab, Barbadoes deposit, Cambridge estate. 
A well-marked species. Cellules all equal, about 7 in 
•OOr'. Marginal strise 16 in -001"'. The arrangement of 
the lines of cellules is very simple. A certain number meet 
in the centre, and these are strictly radiating, forming, as it 
were, a series of compartments within each of which the lines 
take the direction of the inverted letter JS^, one pair within 
another, until the space is filled up, the shortest lines being, 
of course, midway between the tubercles. 
AULACODISCUS. 
Aidacodiscus umbonatus, n. sp,, Grev. — Disc broadly 
umbonate, with a circular umbilicus; processes small, 
numerous (6 or 7) at a short distance from the margin, 
situated in the rounded axils of the nearly linear furrows ; 
