Wallich^ on Siliceous Organisms. 
43 
tally in every point,, the general outline differing only as 
regards the central convexity of the plane margin and the 
absence of the nodule. The same remark applies to Ehren- 
berg^s Triceratium ohtusum, which is akin to Mr. Bright- 
welFs form. {Vide Mikrogeologie/ t. 18 — 49.) 
Stigmaphora^ nov. gen.^ Wall. 
Frustules free, naviculoid. Valves lanceolate, loculate.^^ 
Loculi with central and marginal puncta. 
From the very hyaline nature of this diatom, and its oc- 
curring somewhat rarely, the precise structure of the locu- 
lated portion is perhaps doubtful. The resemblance to 
Mastogloia is apparent, rather than real, for the subjoined 
reasons : — The supplementary nodules, which may be ob- 
served in one species, in the course of the median line, are 
obviously repetitions of the ordinary terminal and central 
nodular processes. Now each " loculus^^ presents a minute 
nodule of precisely similar aspect at its centre. When the 
frustule is seen in a front view, the nodules of the median 
line and the loculi appear in the same plane. It is difficult, 
therefore, to conceive that the one set of nodules should 
belong to the valvular structure, whilst the other forms 
portion of an annular appendage. But, under any circum- 
stances, the nodules of the loculi, and those elsewhere met 
with, afford a marked character whereby this genus may be 
distinguished. 
S. rostrata, n. sp. — Valves lanceolate and suddenly con- 
tracted half-way between the centre and extremities of the 
valve, so as to make the latter seem rostrate. Valve slightly 
inflated at its central margin. Loculi in two pairs. Seen in 
the side view they appear like two small pyriform cells, 
united by their bases, and situated just within the inflation. 
Median line with from three to ten supplementary nodules, 
arranged equidistantly along the rostrate portion of the 
valve. 
Front view, linear lanceolate, truncate at the ends; 
median lines being distinguishable within the valve, and 
parallel to its margins. Length -0038 ; breadth -0006. Figs. 
5 and 6. 
From Salpee, Bay of Bengal and Indian Ocean. April, 
1857. 
>S^. lanceolata, n. sp. — Valves lanceolate, extremities acute. 
Loculi as in first species, but with an additional minute 
nodule on their inner convex margins. Median line without 
