REPORT ON THE DIATOMACEyE. 107 



has no processes of any kind from the valve, which is ornamented with small, ill-defined, 

 thinly placed, almost punctiform granules, which decrease towards the extremities. 



Triceratium ferox, n. sp. (Plate VI. fig. 4.) 



Triangularis ; apicibus cuneato-rotundatis, prominulis ; lateribus rectis ; dentibus non- 

 nullis marginalibus erectis ; valva cellulis vel areolis grandiusculis hexagonis. In mari 

 Japonico. 



This frustule is figured both from its zonal and valval aspects. It is small, triangular, 

 and provided with large hexagonal areolae. Its sides are rectilinear, and its extremities 

 are smooth and slightly prominent. The specific name has reference to the few long 

 teeth or points that are disposed on the sides, and which are probably intended for the 

 union of several frustules into a series. 



Triceratium arcticum, Bright., var. kerguelenensis, nov. (Plate XIII. fig. 7.) 



The specimen here shown must be regarded as a variety of Triceratium arcticum, 

 Bright., 1 as it only differs from that Diatom in not possessing so markedly concave sides. 

 The cellules or areolse are also larger than in the typical specimen. 



Triceratium arcticum, Bright., var. kerguelenensis /3, nov. (Plate XXII. fig. 5.) 



This frustule is also a variety of Triceratium arcticum, Bright. Its radiating rows of 

 granules which spread outwards from the centre, the granules becoming larger and more 

 distinct as they approach the periphery, distinguish it from the Brightwellian species. 



Triceratium arcticum, Bright., var. Icerguelenensis y, nov. (Plate XIII. fig. 5.) 



This triangular form, with concave sides and rounded extremities, was obtained in the 

 neighbourhood of Kerguelen Island. The valve is covered with radiating lines of cellules, 

 which decrease towards the extremities, becoming small granules, arranged in a quincuncial 

 manner. Although thus aQreeinp; in the nature of its cellulation with Triceratium 

 arcticum, Bright., it differs from the latter (1.) in the concave character of its sides, 

 and (2.) in the occurrence of a small central non-granulated or smooth area. These 

 distinctions, however, cannot be looked upon as possessing more than a varietal importance. 



Triceratium calvescens, n. sp. (Plate IX. fig. 1.) 



Grandiusculum, triangulare ; lineis lateralibus concavis ; apicibus rotundatis ; cellulis 

 grandiusculis in lineas radiantes distributis, et ad apices subito in lineolas punctulatas 

 decrescentibus, media valva raris et minuentibus. In mari Japonico. 



This form, like Triceratium arcticum, Bright., is also covered with radiating granules or 



somewhat irregular cellules, which quickly diminish as they approach the extremities, and 



1 = Triceratium wilkesii, var. /?, -with four angles ; Amphitetras wilkesii, Bright-well, Micr. Journ., vol. i. 

 p. 250, pi. iv. fig. 11 ; Roper, Trans. Micr. Soc. Lond., vol. viii. p. 58. 



