NAVICULA FOLLIS. 45 
slightly turgid, obtuse apices; strie fine, transverse, 
distinctly granular, reaching to the median line. 
Kiitzing refers this form to his N. inflata; but it is 
evident that under this name he has included two widely 
different species, one of which (his typical form) he deline- 
ates as unstriated, the other, which he names the variety, 
being striated; the latter is the Pinnularia inflata of 
Rabenhorst (Siissw. Diat.), and apparently identical with 
Navicula inflata of the ‘Synopsis’ and of the present work, 
as will be seen by the synonyms I have given of that 
species. It follows therefore that the typical N. inflata of 
Kiitzing must be reduced to a synonym of N. Follis. 
Rabenhorst, more recently (Europ. Diat.), has reunited 
his P. inflata and N. inflata, Kiitz., with a single descrip- 
tion for both, representing the striz to be from 26 to 80 
in ‘001", and distinctly granular. Mr. Ralfs, on the con- 
trary, states that the strie are absent or indistinct; he, 
however, like Rabenhorst, refers N. Follis to the typical 
N. inflata of Kitzing. I consider N. Follis to be quite 
distinct from N. Trochus, Ehren. 
Hab. Fresh water: rare. Near Heigham, Norfolk (Mr. 
Kitton). I have found it in the Loch-Oich deposit, Cale- 
donian Canal, from which the specimen figured was 
obtained. 
Subsection VIII. Valve divided into two lobes by a median sinuous 
constriction ; strice reaching to the median line, but divided 
into two sections by a longitudinal groove. 
This subsection comprises the genus Diploneis of Ehren- 
berg. Although an exceedingly natural group, its members 
are not distinguishable from the Navicule by any decided 
generic characters. They are all recognized by two essen- 
