REPORT ON THE DIATOMACE.E. 29 



the forms just named, being less sinuately incurved than the former and somewhat more 

 so than the latter. All three possess transversely disposed continuous stria) which are 

 parallel to each other in the middle, but are directed in a radiating manner at the 

 extremities, and in all the stria? are interrupted by two longitudinal furrows, while their 

 central extremities are placed in close proximity to the raphe. Such considerations point 

 to the conclusion that we have here a form which is very probably identical with the 

 Navicula grunowii of Eabenhorst. 



Navicula janischii, n. sp. (Plate XXX. fig. 5.) 



Biloba, profunde constricta, lobis cuneato-subcordatis ; structura dense et inordinate 

 granulata ; plicis a margine radiantibus, hinc evanescentibus. Ad insulas Bermudas. 



This frustule, from the neighbourhood of the Bermudas, possesses an exceedingly elegant, 

 bilobed form. The lobes are subcordate and cuneiform, and the margins are marked by a 

 row of well-defined dots, while the surface is irregularly granulated and carries radiating 

 lines which proceed inwards from the periphery but become indistinct and disappear before 

 reaching the raphe. 



It bears a considerable resemblance to a frustule from Samoa which occurs in 

 a superb preparation by Moller, but in the latter the middle plica is absent and the 

 granulations of the surface are much less marked. It is also somewhat similar to the 

 Navicula jamaicensis described by Greville, but in the Grevillean species the points or 

 granules are disposed regularly instead of being agglomerated without order. 



This new species is named in honour of Mr Charles Janisch the Diatomist. 



Navicula bullata, Norman, var. carinata, nov. (Plate XXVIII. fig. 7.) 



The specimen here represented is evidently closely related to the Navicula bullata 1 

 of Norman. This is indicated by its elliptical form, its obtuse apices, and by the radiately 

 disposed rows of granules, which are interrupted by two distinct bands upon which a small 

 number of large rounded dots occur. 



The apices of the frustule are clearly hollowed and the valves are longitudin- 

 ally plicated ; the longitudinal bands do not present any constriction in the centre, and 

 the granules are much less numerous than those of Navicula bullata. 



Navicula bullata, Norman, var. obtusa, nov. (Plate XXVIII. fig. 10.) 



This frustule is elliptico-rhomboidal and not simply elliptical like that established by 

 Norman, nor, and this is a matter of greater importance, are the apices of the former in 

 any way elongated or sub-produced, but are merely rounded. The significance of this fact 

 becomes more apparent when it is borne in mind that, among navicular Diatoms in 



1 Micr. Joum., 1861, p. 8, pL ii. fig. 7. 



