Greville^ on New Diatoms, 
101 
Hemiaulus. 
Hemiaulus crenatus, n. sp._, Grev. — Valve in front view 
with the angles produced into minute subconical horns; 
median space elongated, slightly convex, with numerous cre- 
nations ; structure very minutely punctate. Breadth of frus- 
tule -0037". (Fig. 12.) _ 
Hab, Barbadoes deposit^ Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. ; very rare. 
Quite unlike any of the other species obtained from the 
same deposit. In the perfect frustule now before me the 
two valves united only measure 'OOO?^' in the centre, and 
from the suture to the apex of the horns is under •0004"". 
Number of crenations 17, but this character doubtless varies 
according to the age (?) of the frustule. 
Hemiaulus minutus^n. sp., Grev. — Minute; valve in front 
view with the angles produced into very minute short horns, 
tipped with a short spine ; median space divided into three 
equal parts, the central one convex, with 2 transverse costse 
reaching to the suture; structure minutely punctate. 
Breadth of frustule -0014". (Fig. 5.) 
Hab. Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
The minute horns are rather slender and the spines ex- 
tremely small. The punctation of the valve is not crowded. 
Triceratium. 
Triceratium figiiratam, n. sp., Grev.— -Minute ; valve with 
concave sides, and broadly ovate rounded angles; margin 
broad, continuous, with a few remote strong striae ; central 
area defined by lines cutting off so much of the angles as to 
leave only a minutely punctate triangular space; angles 
within filled with minute puncta. Distance between the 
angles -0012". (Fig. 15.) 
Hab, Barbadoes deposit, Cambridge estate ; in slides com- 
municated by C. Johnson, Esq. 
A beautiful little species, about the size of T. brachiatum, 
and totally unlike any species I am acquainted with. 
Triceratium brevinervum, n. sp., Grev. — Minute; valve 
with strictly straight sides and subacute angles, each of which 
is bounded interiorly by two short, marginal, vein-like lines ; 
central area with small, scattered, remote puncta; angles 
filled with more minute and more crowded puncta. Distance 
between the angles -0022''. (Fig. 26.) 
