44 (treville, on New Diatoms. 



I have much pleasure in dedicating this remarkable and 

 ornate species to my friend, Mr. TufFen West, the unrivalled 

 illustrator of the Diatomaceae, and Avho is well acquainted 

 with the nature of the objects themselves. It is allied to 

 Triceratiam castellatum, described by himself, from the same 

 deposit, in the eighth volume of the ' Transactions of the 

 Microscopical Society ;' but is, in several important cha- 

 racters, perfectly distinct. Like most of the species of Tri- 

 ceraiia discovered in this mine of novelties, it is excessively 

 rare. I have only met with six specimens. 



Triceratium Barbadense, n. sp., Grev. — Sides of the frustulc 

 gently concave ; angles broadly rounded, separated from the 

 centre by transverse lines ; whole valve closely and minutely 

 punctate. Distance between the angles -0016''. (Fig. 12.) 

 Hab. Barbadoes deposit ; excessively rare- 

 Allied to T. castellatum, but differs in the form ; the sides 

 of the valve not being nearly so deeply concave, and the 

 angles, instead of swelling into segments of circles, being 

 merely broadly rounded. 



Triceratium nitiduin, n. sp., Grev. — Sides of frustulc rather 

 deeply concave, angles ovate, separated from the centre by 

 transverse lines ; whole valve punctate; puncta of the central 

 space radiating, and becoming conspicuous as they reach the 

 margin. Distance between the angles, •0014". (Fig. 13.) 



Hab. Barbadoes deposit; extremely rare. 



I am not aware of any described species for which this can 

 be mistaken. A good character exists in the puncta of the 

 centre, which radiate in single lines, becoming gradually 

 larger and the lines more distinct as they approach the 

 margin. 



Triceratium cellulosum, n. sp., Grev. — Sides of the valve 

 straight ; angles with pseudo-nodules, obtuse, separated from 

 the centre by transverse lines ; centre and angles coarsely 

 and irregularly cellulose ; cellules of the former more or less 

 ovate or oval, and disposed in a radiating direction, though 

 not in lines ; those of the latter in rows parallel with the sepa- 

 rating line. Distance between the angles •0026". (Fig. 14.) 



Hab. Barbadoes deposit ; exceedingly rare. 



Large and robust, as compared with many of the Barbadoes 

 species ; and so peculiar in its characters as to be instanta- 

 neously recognised. The cellules of the angles are somewhat 

 quadrate, and hence those parts of the valve have a sort of 

 cancellated aspect. The lines which separate the angles 

 from the central area appear as linear spaces left unoccu- 

 pied by the cellules. 



Murrayfield, Edinburgh; January 15th, 1861. 



