GrevillEj on New Diatoms. 75 



circular space, minutely punctate. Distance between the 

 angles -0026". (Fig. 4.) 



Hab. Barbadoes deposit; excessively rare. 

 In general outline this species bears a close resemblance to 

 T. productum of my Series II, but differs essentially in the 

 absence of all vein-like lines. From T. capitatum of Ralfs it is 

 removed by the much larger size, shorter angles, the absence 

 of spines, and by the minute and close punctation of the 

 whole surface. 



Triceratium insignis, n. sp., Grev. — Large. Valve with con- 

 cave sides, and broadly rounded angles, furnished with 

 minutely punctate pseudo-nodules ; surface filled with radiat- 

 ing lines of minute, distinct granules, except a small, central, 

 blank space; margin with short, broad strise, 9 in "OOl". Dis- 

 tance between the angles •0034. (Fig. 5.) 



Hab. Barbadoes deposit ; excessively rare. 



A remarkably fine and ornate species, possessing most dis- 

 tinctive characters. At first sight the angles have the appear- 

 ance of being separated from the centre by a transverse line, 

 but this is not the case. The efiect is produced by the radiat- 

 ing lines of granules cui-ving up the prominent angles, and 

 being viewed, as it were, in prospective, the extremities of the 

 lines form a transverse row of dark points. A very con- 

 spicuous feature in the valve is the termination of what are 

 doubtless strong, broad striae in the front view,' and which are 

 curved over the edge of the valve in the side view. The ra- 

 diating lines of granules which closely cover the surface do 

 not quite reach the margin, but leave a narrow, blank space. 



Triceratium rotundatum, n. sp., Grev. — Small. Valve with 

 deeply concave sides and broadly rounded angles, the ends of 

 which are filled with minute puncta, bordered with a few 

 larger ones; centre blank, surrounded by an irregular, tri- 

 angular band of still larger granules, between which and the 

 granules of the angles is a transverse, blank space ; concave 

 margins, with a few distant, large granules. Distance between 

 the angles -0020". (Fig. 6.) 



Hab. Barbadoes deposit; extremely rare. 



About the size of T. castellatum, and T. Westianum ; but 

 the angles do not form segments of circles as in those species, 

 being merely broadly rounded. About six granules compose 

 the marginal row in the concavities of the valve. 



Triceratium amcenum, n. sp., Grev. — Small. Valve with 

 straight sides and rounded, incrassated angles ; centre some- 

 what convex, with subremote radiating puncta, which gradu- 

 ally increase in size from the centre to the circumference. 

 Distance between the angles about -0024". (Fig. 7.) 



