42 NOVARA DIATOMS. 



of the median line ; median and central nodnles oblong ; stria? 

 reaching median line, delicate, 50 in. -001". [PI. 2. f. 16, a 5.] 



Bergmehl, Java. 



Distinguished by the well-marked undulating sub-marginal lines 

 from any other species of Navicula. (The outline of the valve 

 and the undulating lines seem to show some affinity with the 

 genus Cylindrotheca, a genus, however, with which I am only ac- 

 quainted by name. F. K.) 



Navicula pacifica, Grun.— This form is not described in the 

 text. [PI. 2, f. 17.] 



Pleurosigma austxale, Grun., n. sp.— Small, narrow, lanceolate, 

 sub-sigmoid ; apices somewhat acute ; median line gracefully 

 sigmoid; central nodule round,* striae oblique, delicate, 55 — 60 ; 

 colour of dry frustule yellowish-brown. [PI. 2, f. 18.] 



On Ballia Callitricha, from New Zealand. 



Resembles P. JEstuarii, but is smaller, and not of the pale purple 

 of that species, but a yellowish-brown. And as it can be compared 

 with no other of Smith's species of Pleurosigma, I am reluctantly 

 obliged to describe this uncharacteristic species as new. 



Diadesmis confervacea, KuU. Bacill. T. 1, /. 8.— [PI. 2. f. 19, a. 

 b.~] Amongst Cladophora Roettleri, Kiitz. and fresh water. Rio 

 Janiero. 



The valves closely enough resemble Kiitzing's fig. and descrip- 

 tion to warrant our referring this form to Kiitzing's species. 



The strias are 56 to 60 in. -001". 



D. peregrina, W. Smith, Ann. of Nat. His.— [PL 2, f. 20, a b.~] 

 Tahiti. 



The specimens from Kew Gardens, London, have enabled me to 

 obtain a view of the valve, and I am satisfied of their identity with 

 the Tahitan form. 



As this species is but little known I have given figures of valve 

 and filament. 



The valves are stout, ovate, sometimes nearly rhomboid, often 

 with slightly produced apices ; median nodule distinct. The striae 

 are delicate, above 60 *001. 



It resembles Navicula brachysira, Breb., and it must not be over- 

 looked that this form also occurs in short filaments, produced by 

 the cohesion of the smaller valves. 



CRATICULA, Grun., Gen. Nov. — Frustules naviculoid, valves 

 double, outer valve ? furnished with central and terminal nodules, 

 punctatostriate ; interior valve surirellseform, costate ; costaa linear, 

 distinct, reaching median line, for the most part wanting from the 

 central portion, 



Cxaticula Perrotettii, Grun., n. sp.— Valve lanceolate ; apices 

 shortly produced, obtuse ; longitudinal lines distinct, 24 in. -001" ; 

 transverse, 48 in. -001", costaa 7-4 in. -001" [PI. 2, f. 21, a in- 

 ternal valve, b external do.] 



From Senegal, amongst Nitella, Perrotet. 



