AMPHORA. 



I2 5 



GENUS I. AMPHORA EHR, 1831. 



I bis 



1 



Frustules generally free, solitary, oval, oblong, elliptic oval or 

 sub-quadrangular, often inflated or constricted in the girdle view. 



Valves cymbifurm, with central 

 nodule marginal or sub-marginal, 

 often dilated into a stauros, raphe 

 often inflated. Connecting zone often 

 longitudinally striate, plicate, or 

 punctate. 



Endochrome formed by a single 

 layer, the middle of which rests on 

 the dorsal, connecting zone, and 

 ra covers over the two adjacent valves 

 and the other side of the zone, in 

 the middle of which is found the 

 line of separation. 



A large number of Amphora are 

 " complex." Those are so named whose 

 connecting zone contains a more or 

 less considerable number of cuneate seg- 

 ments which have been, somewhat justly, 

 compared to slices of melon. These 

 segments have sometimes a structure or striation analogous to that o 

 the exterior segments (valves) but have neither raphe nor nodules ; 

 at other times however the striation of the interior segments is 

 different. 



The genus Amphora is one of the most difficult genera of diatoms, 

 and it is also one of the most extensive, as authors have placed in it 

 more than 200 species. Prof. H. L. Smith was the first to elucidate 

 the structure of Amphora by demonstrating that the genus originated 

 from Cymbella by the unequal development of the two sides of 

 the connecting zone. Figure 24 a is a diagrammatic section of an 

 Amphora showing at the same time the disposition of the layer of 

 endochrome. 



In the arrangement, in this Work, of the genus Amphora, the classifi- 

 cation of Prof. Cleve has been followed. The sub-genera and the list of 

 species are given in accordance with the manuscript documents kindly lent by 

 the learned Professor. 4j 



Fig. 24. 



a Diagrammatic section of Amphora. 

 b Amphora ajfinis, valve view. 

 c Amphora ovalis, girdle view. 



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