Diatomacese from the Caspian Sea. By A. Grunow. 681 



NlTZSCHIEiE. 



[We omit the remarks of the author on this family, as we hope 

 his monograph will be in the hands of the diatomist ere long. 

 He unites the genus Tryblionella with Nitzschia, remarking that 

 " long observation of this genus (Nitzschia) had convinced him that 

 the genus Tryblionella was not sufficiently distinct to warrant 

 their separation ; " he therefore relegates the following forms to 

 the former genus. — F. K.] 



T. Hantzschiana Grun., T. gracilis W. Sm. = N. Trtjblionella 

 Hantzsch. T. Victoria Grun. and T. levidensis AV. Sm., he 

 considers to be only varieties of that species. Baku Harbour. 



T. jyundata W. Sm. Baku Harbour. 



T. apiculata Greg, [not W. Sm. as stated by Grunow]. 



T. eircumsuta Bailey = Surirella circumsuta Bailey = T. 

 Scutellum W. Sm. Common in Baku Harbour. 



The valves of this species have a longitudinal ridge (langsfaltig), 

 but the transverse striee are not interrupted by it as they are in 

 many other species. By direct light the surface of tbe valve 

 appears irregularly punctate (shagreen-like) ; this is still more 

 conspicuous in the closely allied form Nitzschia Brightivellii 

 (Kitton), in which it is clearly shown that the large puncta 

 and the fine regular lines of striae belong to different layers of the 

 valve. 



[The stria3 on T. circumsuta and N. Brightwellii have a certain 

 family resemblance, but the structure of the valve is conspicuously 

 different in the former species. Close to the punctate margin runs 

 a longitudinal V-shaped furrow, forming a ridge near the centre of 

 the valve, which gradually descends towards the margin ; a section 

 made across the centre of the valve would be something like three- 

 fourths of the letter W, W . This peculiarity is more or less visible 

 in all the Trybhonellae. Nitzschia Brightu-ellii has the surface of the 

 valve flat, like all the true Nitzschias. T. circumsuta is elliptic 

 lanceolate. N. Brightwellii is linear lanceolate. — F. K.] 



Nitzschia Sigma W. Sm. var. interceclens Grun. Length, 

 *2 mm. ; breadth, -0065 mm. Keel puncta, 7 in -01 mm. 



N. Sigma embraces a great number of forms, the extremes of 

 which would not with certainty be relegated to one species were it 

 not that so many intermediate forms exist between them. The 

 following are the principal : — 



Var. ? maxima Grun. Length, • 9 mm. ; breadth, • 9 mm. ; 

 keel puncta, 3-4 in -01 mm.; transverse stria3, 15-18 in 

 •01 mm. 

 Var. valida Grun. Length, -5 mm. ; breadth, -017- '022 ; 

 keel puncta, 3i-5 in '01 mm. ; transverse striae, 18-21 in 

 •01 mm. 



