72 Greville, on New Diatoms. 



occur. This diatom is subject to occasional distortion, 

 several examples having occurred to me in which the sides 

 were of very unequal lengths. 



Tricet'atium Bi'owneanum, n. sp., Grev. — Small; valve with 

 straight sides and rounded angles with obscure pseudo- 

 nodules ; surface filled up with small, round, equal, irregularly 

 disposed granules. Distance between the angles about 0020". 

 (Fig. 16.) 



Hub. In mud, Savannah, Georgia, U.S. 



Probably not a rare species, as it occurs tolerably abundantly 

 in a slide kindly communicated to me by my friend, Mr. 

 George Mansfield BroAvne, of Liverpool. It is well marked 

 by the equal size throughout the entire valve of the round 

 granules, which, although not crowded, are rather closely 

 situated. The angles are thickened, but can scarcely be said 

 to possess a pseudo-nodule. 



Triceratium ? blanditum, n. sp., Grev. — Sides of valve deeply 

 concave ; angles broadly rounded ; centre with a small, blank 

 space; granules conspicuous, subremote, equal, forming 

 straight, equidistant, parallel lines. Distance between the 

 angles in the four-angled frustule 0020". (Fig. 17.) 



Hah. Barbadoes deposit ; excessively rare. 



A very striking object, which I introduce with some hesita- 

 tion as a Triceratium. Amphitetras, however, is now ad- 

 mitted to be separated from that genus by a very slender 

 line. I have seen only two frustules, both of which are 

 four-angled, and very conspicuous for the equal size of the 

 granules, their equidistance, and the perfectly straight, 

 parallel lines in which they are arranged. The small, circular, 

 blank space is only defined by the absence of granules. 

 There is also a small, vacant space opposite to each concavity 

 of the valve. This species may have some affinity with 

 Amphitetras parallela of Ehrenberg, found in a fossil state 

 in Greece. 



COCCONEIS. 



Cocconeis Grantiana, n. sp., Grev. — Very minute; valve 

 elliptic, smooth, with a slender median line and nodule, the 

 margin furnished with a moniliform row of large, oblong 

 granules. Length -0011". (Fig. 18). 



Hab. On marine shells, Macduff; John Grant, Esq. 



A beautiful little object, the smooth disc rendering the 

 marginal row of brilliant, bead-like granules more conspicuous. 

 Mr. Grant, to whom I am indebted for a specimen, aptly 

 compares the entire frustule to a jeweller's ornament set 

 with gems. 



