3 8o 



HANTZSCHIA. 



Valve suborbicular, with margin showing narrow costal, approximate, 

 commencing with a bead and about 160 in number in a valve (about 5 in 1 

 c.d.m) ; median area covered with a delicate network and showing a narrow 

 pseudo-raphe. Diameter, 7 to 1 2 c.d.m. 



Marine. Scotland (Gregory) ; France ! 



C. HmbatUS Breb. (Diat. Cherb., p. 12, f. 1 ; Deby., pi. 10, f. 62* ; 

 plate 32, fig. 873. 



Valve orbicular, with a circlet of costs, very short, approximate, of almost 

 equal thickness throughout their length, 3 in 1 c.d.m., and showing in each 

 interval two rows of fine puncta ; median area almost smooth at the central 

 portion, with margin showing 3 or 4 rows of fine puncta, concentric. 



Marine. Coasts of Scotland and of France, and probaby in other portions of the North Sea. 



COHORT IV.-NITZSCHIINE^. 



TRIBE XVIL NITZSCHIE^;. 



f 1 Keel diagonally opposite in the two valves . Nitzschia. 



j r rustules free. -, j^ ee ] f tne two va i ves placed on the same side of 

 '. ( the frustule .... Hantzschia. 



[_ Frustules enclosed in mucous sheaths .... Homceocladia. 



GENUS 80. HANTZSCHIA GRUNOW, 1877. 



Valves arcuate, with rostrate apices, fur- 

 nished with a keel having short dots, pro- 

 longed into short costae, or traversing the 

 entire valve ; between the two median dots is 

 found the rudiments of a nodule. Girdle face 

 showing keels placed on the same side of the 

 frustule. 



Fig. 123. 



Hantzschia ampfiioxy: 



