36^ DESCEiPTioN OF IPoli/ffastriea. 



due to the minute size of the specimens under my notice, as I have 

 occasionally observed veiy faint lateral striae. A fiaistule of this 

 species, though veiy much smaller, has a great resemblance to a 

 soKtaiy one of Fragilaria pectinalis ; but in this plant the concavity 

 of one margin is generally gi'eater, and the constriction near the 

 ends of the frustules more considerable ; the front view, too, is 

 nan'ower in proportion to the lateral ; stiU it may eventually prove 

 to be only the commencement of that plant." 



This is probably identical with E. monodon of Ehrenberg.. 



Genus Euronisctrs. — Lorica simple, valves equal, orbicular, not 

 concatenated; unilocular, furnished with tubular processes, per- 

 forated at the apex, projecting from near the margin. 



The number of tubules was at first employed by Ehrenberg as a 

 generic characteristic, but he now assigns to it but a specific value. 



Eupodiscus is therefore equivalent to the previously-named genera, 

 Tripodiscus, Tetrapodiscus, and Pentapodisciis. 



E. Germanicus. — Has three tubular processes, and eighteen cells 

 in 1 -1200th. The lorica large, orbicular, and rather compressed; 

 cells in radiating series ; processes short and hyaline. Colour green. 

 Cuxhaven. (P. 14, f. 41, 42.) 



E. qiiaternarnis. — Foirr appendages. 



E. quinarius. — Five processes. 



E. momtruosus. — Pour processes on one side. Diameter 1 -240th. 



E. Roger sii. — Has six appendages round its periphery ; valves 

 with four-and-a-half large cells in l-1200th., together with five 

 radiating series of granules, ten in 1-1 200th. Diameter 1 -204th. 

 Vu-ginia. 



'E. Baileyi. — Seven processes around its circumference. Virginia. 



E. radiatiis (Bailey.) — In form, size, and reticulation, resembling 

 the Coscmodiscus radiatus of Ehrenberg, but having foiu" (or more) 

 foot-like projections near the margin. A common form in the 

 Southern States of America. 



Genus Feagilaria. — Lorica simple, bivalve or multivalve, prismatic, 

 having a general resemblance to Nwvicula ; striated on the sides, 

 leaving a central clear portion. In most species each extremity is 

 furnished with two openings ; these being in the same plane, the 

 surfaces upon which the chain rests may be considered lateral, and the 

 self-division will then be dorsal. The whole chain sometimes rises 



