[REPORT ON THE BIATOMACEjE. 157 



must for the present remain a matter of doubt, although the dissimilarity of the valves, 

 the very delicate striation, and the radiating rows of denticules seem to point to the latter 

 alternative. It may, however, in the meantime be treated as a species which provisionally 

 ranks among the Coscinodisci. 



Coscinodiscus (?) janus, n. sp. (Plate II. fig. 2.) 



Valvis dissimilibus, vix conspicue striatis et denticulorum lineis a margine excuntibus, 

 in una valva subdensioribus, in altera rarioribus centrum attingentibus vel prius aut 

 postea cessantibus ; ad marginem ambae decern distinctioribus granulis notantur. Ut supra. 



The two dissimilar valves here figured must be regarded as forming a single species, 

 which is, however, to be looked upon as a doubtful member of the present genus. The 

 valves were found in the same preparation as that in which Coscinodiscus (?) bifrons 

 occurred, and they possess the same characteristic radiating lines of small, salient puncta, 

 which proceed from the margin towards the centre, while they also exhibit two distinct 

 systems of striation. The margin of each valve, however, is ornamented by eight equi- 

 distant points, or, perhaps, little protuberances, and, as in Coscinodiscus (?) bifrons, the 

 perimeters of the two exactly coincide. 



Coscinodiscus (?) dimorphus, n. sp. (Plate XVII. fig. 6.) 



Minimus ; valvis irregulariter, una rarius, altera crebrius punctulata (denticulata). 

 In Atlantico meridionali. 



This very minute disc also possesses valves which are dissimilarly granulated, and might 

 therefore be regarded as belonging to distinct species, or at least to varieties of one species. 

 They, however, belong to a single frustule which was collected in the South Atlantic. 



Coscinodiscus comptus, n. sp. (Plate XIII. fig. 9.) 



Forma discoidalis plurimis punctulorum lineis circumradiantibus, quorum nonnuUae 

 prope centrum, reliquse ad medium radii vel circiter evanescunt. In mari Antarctico. 



This elegant small disc is probably closely allied to the preceding. It is surrounded 

 at the periphery by numerous radiating striae of small points, the majority of which proceed 

 only a short distance towards the centre, while a few reach the margin of a smooth but 

 small central areola. Although the aspect of the granular lines and the delicacy of the 

 striation present obstacles in the way of regarding this form as a Coscinodiscus, it may 

 for the present be enrolled in that genus. Its specific name has reference to the elegance 

 of its sculpturing. 



Coscinodiscus antarcticus, n. sp. (Plate XII. fig. 10.) 



Forma parva, inordinate punctata, et raris spinulis circumfusa. Ad meridiem insula? 

 Heard. 



