Diatomaceai from the Caspian Sea. By A. Griinow. 679 



Navicule^. 



NavicuJa Trochus Ebr. var. hieonstrida Gran. — Valves with 

 three equal stout inflations, and slightly produced obtuse apices 

 •042 mm. long. Inflations '001 mm. (this should be "01); con- 

 strictions -006 broad. Striae transverse (18-20 in '01 mm.), 

 radiant at the centre, two large thickened sickle-shaped lines on 

 each side of the central area. 



Eare in Baku Harbour. 



Although of very difierent form it appears nevertheless to belong 

 to the series of which N. Trochus is the type, but which has only 

 one central inflation. I have, however, many forms before me in 

 which the ends are produced and a couple of slight depressions are 

 visible, evidently showing a transition to the above described ex- 

 treme variety. Characteristic of N. Trochus is the circular smooth 

 space round the central nodule, and which has the two sickle- 

 shaped forks on each side. 



[N. Trochus of authors is not N. Trochus of Ehrenberg accord- 

 ing to Dr. Donkin. A careful examination of the figures of 

 N. Follis in the ' Mikrogeologie ' will show that what has generally 

 been considered N. Trochus is probably N. Follis. Dr. Lewis, in 

 his paper on " Extreme and exceptional Variation of Diatoms," 

 also refers the so-called N. Trochus to N. Follis* (Professor 

 H. L. Smith concurs in this view), but considers it to be only an 

 extreme variety of N. serians, a view with which I am disposed to 

 agree. The variety described by Herr Grunow I think more 

 nearly resembles N. trinode of Lewis, I. c. nee Smith, and which he 

 says is found in large rivers and brackish water, whilst N. Follis 

 is only found in fresh. — F. K.] 



N. Schneicleri Grun. — N. major, valvis lanceolatis obtusius- 

 culis, nodulo centrali oblongo, nodulis terminalibus minutis, sulcis 

 duobus lineae medic's approximatis longitudinalibus, striis punctatis 

 obliquis varie arcuatis 14 in '01 mm. longitudinalibus 13 in 

 '01 mm. Longit. '143- '145 mm.; latit. '042 '043 mm. 



Eare on the pier of Cape Bail. 



A well marked Navicula ; on each side of the median line is 

 a conspicuous line of coarse striae, between which and the striae 

 is a narrow, smooth furrow, connecting it with the subsection 

 Diploneis, but distinguished from it by the striae which cross the 

 valve in curved obhque lines resembling those on iV. ohlique- 

 striata A. Schmidt, Demerara Eiver. Atlas, pi. 13, figs. 41, 42. 



[N. Iridis has a similar striation. — F. K.] 



* The figure, in the ' Infusionsthierchen,' of N. Trochus is certainly very like 

 what is usually known by that name ; the probable solution is that they are both 

 one species. 



