70 Greville, on Nev) Diatottis. 



angles produced, capitate ; centre divided into compartments 

 by radiating, vein-like veins. Distance between the angles 

 •0027". (Fig. 9.) 



Hab. Barbadoes deposit ; excessively rare. 



This beautiful species is evidently related to T. truncatum 

 and T. venosum ; to the former very closely, Avhile, at the 

 same time, it is abundantly distinct ; the truly capitate, pro- 

 duced angles taking the place of the broad, truncate angles 

 of that diatom. 



Triceratium inconspicuum, n. sp., Grev. — Minute, sparsely 

 punctate; angles of the valve semicircular, subtruncate, 

 separated from the centre by a transverse line ; centre 

 bordered with a row of puncta. Distance between the angles 

 •0005". (Fig. 10.) 



Hab. Barbadoes deposit ; excessively rare. 



Of this exceedingly minute species I have seen half a 

 dozen specimens, all of which have four angles. In its cha- 

 racters it comes very near to some varieties of T. brachiatum, 

 but is separated by its size alone, which scarcely exceeds 

 that of T. exiguum. 



Triceratium delicatum, n. sp., Grev. — Minute ; valve with 

 slightly concave sides and broadly rounded angles filled up 

 with transverse rows of fine puncta; centre containing a 

 pale, obtusely triangular band, within which is a triangular 

 spot, bordered with puncta. Distance between the angles 

 •0012''. (Fig. 11.) 



Hab. Barbadoes deposit ; excessively rare. 



A minute species, difficult to define in few words. The eye 

 is first impressed with the pale (blank), triangular band, 

 which exactly fills up the centre of the valve by the angles 

 reaching to the concave margin, and, consequently, separating 

 the angles of the valve from the parts within. In the central 

 spot, which is edged with a row of distinct puncta, I have 

 been unable to trace any particular structure. A peculiar 

 feature in this little diatom is a considerable space between 

 the sides of the pale band and the transverse rows of puncta 

 which occupy the angles. These puncta also gradually de- 

 crease in size as they approach the apex. 



Triceratium labyrinthceum, n. sp., Grev. — Valve with 

 rounded angles and somewhat convex sides, the centre 

 having a network of flexuose, widely anastomosing, vein-like 

 lines, the inclosed spaces being finely punctate. Distance 

 between the angles -0023". (Fig. 12.) 



Hab. Barbadoes deposit ; excessively rare. 



Of all the curious Triceratia which have been discovered 

 in this inexhaustible deposit the present species is one of the 



