364 DESCKIPTION OF \^Polygash-ica. 



shorter bands belong to Ehrenberg's Fragilaria rhabdosoma; p. 17, 

 fig. 3 is F. hipunctata ; figs. 4 and 1 2 is F. diophthalma ; figs. 2 and 7 is 

 F. Scalaris ; figs. 5 and 8 is F. mtdti2}uncfata ; fig. 9 is F. Jissa ; 

 whilst figs. 10, 11, and 6, represent the F. tenuis of Agardh." 



Feagilakia grandis. — Striated, lanceolate ; laterally, ends obtuse. 

 As many as thirty frustules often cluster in a single band. (P. 3, 

 f. 171.); striae 11 in l-1200th. Length of single rods or frustules 

 1-5 70th. to l-120th.; vide F.pectinalis (Ralfs.) 



F. Glans. = Navicula (? ) glans (Ehr.) — Short, striated, expanded 

 in the centre, so as to recal the figure of an acorn ; ends constricted, 

 obtuse. Stiia) two to three in 1-1 200th. Fossil. Length 1-1 150th. 

 to 1 -570th. 



F. scalaris. Tlie ladder-lilce Fragilaria. — Smooth, seven to eight 

 times longer than broad ; granules of a fallow hue. Breadth of 

 band («. e. length of fnistule) l-860th. to l-570th. 



F. diopliiliahna. — Smooth, three to four times longer than broad ; 

 granules (ova, Ehr.) of a golden yellow coloiu', disposed iu ten 

 portions. Length 1 -960th. to 1-1 150th. 



F. pectinalis. — Striated, two to six times longer than broad ; 

 dilated and lanceolate on the lateral surface ; striae eight in 

 l-1200th, ; granules yellow. In^e living state the striae are very 

 indistinct. (P. 3, group 1 76, a band, and the side view of a single 

 ftaistule.) Common in ponds. Length l-2200th. to l-430th. 



F. rhabdosoma. — Smooth, slender, and fi'om five to twenty times 

 longer than broad. The extremities of the unsti'iated lateral surfaces 

 are needle-shaped. In some chains, the specimens are imited 

 together firmly ; in others, the bands easily drop to pieces, the portions 

 detached exhibiting locomotion, and may easily be mistaken for 

 Synedra or NavicuJa ; but the number and position of the openings 

 are the distinguishing marks, (figs. 173, 174.) They are pale 

 brown when recent, when dried greyish. Living in fresh water, 

 fossil at Cassel. Length 1-5 70th. to 1 -200th. 



F. twrgidula. — Striated, and from two to three times longer than 

 broad, as seen in group 1 72 ; margin with many dentations ; striae 

 six to nine in 1-1 200th.; on secondary side lanceolate and rather 

 obtuse. Length l-720th. to l-570th. Berlin. 



