86 Greville. on New Diatoms. 



Triceratium nebulosum, n. sp.^ Grev. — Valve with concave 

 sides and broadly rounded angles, the ends of which are 

 filled with a cloud of minute puncta ; centre occupied with 

 an indefinite cluster of small puncta, while larger ones are 

 remotely scattered over the rest of the space. Distance 

 between the angles -0032". (Fig. 15.) 



Hab. Barbadoes deposit j exceedingly rare; George Nor- 

 man, Esq. 



This species bears some resemblance in general outline to 

 T. trisulcum of Bailey, figured in Pritchard's ' Infusoria,^ 4th 

 edit., pi. viii., fig. 27 ; but there are no transverse lines 

 separating the angles from the centre. It is otherwise nearly 

 allied to the same diatom, in the angles being crowded with 

 minute puncta and in those of the centre being remotely 

 scattered. These latter, however, are more numerous than 

 in Professor Bailey's species, and there is, besides, a marginal 

 line of irregularly disposed and more closely approximated 

 puncta in the concave sides of the valve. It is also allied to 

 my T. rotundatum, a much smaller species, from which it 

 diff'ers in the sides being much less deeply concave, in the 

 absence of the single lateral row of large granules, and in the 

 arrangement of the central granules generally. 



Amphiprora. 



Amphiprora conspicua, n. sp., Grev. — Front view broadly 

 winged, much constricted, truncated at the ends; a row of 

 linear nodules at some distance within the margin; striae 

 conspicuous, about 18 in -001". Length -0046". (Fig. 16.) 



Hab. Sierra Leone, F. Kitton, Esq. 



The finest species, perhaps, of the whole genus ; allied to 

 A. alata, but quite distinct. In the first place, the frustule 

 is far from being equally hyaline ; and instead of the striae 

 being perceived with some difiiculty, they are rather coarse 

 and very conspicuous. Then, in A. alata the number of 

 striae (which I have been unable to ascertain satisfactorily for 

 myself) is given by Smith as 42 in "001", which is adopted 

 by Ralfs in the last edition of Pritchard's ' Infusoria ;' but in 

 our new species they may be set down at 18 in "001 ", I 

 have found them vary a little, but I assume this number as 

 the average. Again, a certain number of the striae swell into 

 a sort of linear nodule at some distance within the margin, 

 and the line thus formed, following the marginal curve, con- 

 stitutes a most peculiar and striking character. There seems 

 to be no fixed rule as to the pi'oportion of striae which exhibit 



