412 DESCRIPTION OF \Toly(jasiripa. 



Navicula Formica. — Oblong, linear dorsally ; constricted in four 

 places ; segments oblong. Marine in United States. 



N. Fusidiuvi.' — Large, nairowly lanceolate on back, slightly con- 

 stricted at the ends, which are rounded and capitate. 



N. mtchcockii. — Dorsally broadly linear, oblong; laterally con- 

 stricted in two places, thus producing throe equal projections ; ends 

 suddenly cuneate, subacute. Massachusetts. 



N. Iridis. — Large, elongated, bacillar ; sides plane ; apices slightly 

 attenuated, obtuse ; surface very finely striated longitudinally, causing 

 it to display various colours. If sui generis (?) New York. 



N. leptogongyJa. — Smooth, small, linear, slender; a central round 

 protuberance on the back ; ends obtuse, rounded, rather dilated. 

 Thun and Labrador 



N. leptorhyiichus.—^vaH)! ; dorsally, linear lanceolate ; ends very 

 long, rostrate, straight, subacute. Approaches N. dirhjncus, but 

 ends longer rostrate. Mexico. 



!N . limbata. — Small, linear dorsally ; sides sti'aight ; internally, as 

 if widely bordered (limbate) ; apices suddenly constricted, but trun- 

 cate. Chili. 



N. Uneolata. — Small ; on dorsum narrowly lanceolate, with longi- 

 tudinal fine lines ; ends acute ; on side widely linear. Length 

 1 -288th. Freshwater. 



N. Lyra. — Larger, broadly elliptic-lanceolate ; ends constricted, 

 obtuse ; surface with a central double raised band, in the form of a 

 lyre of two cords. Falkland Islands. 



K. nn,esolepia. — Linear, elongate, undulate on back, slender ; 

 three undulations at the centre ; ends much constricted, rostrate, 

 obtuse. Length 1 -420th. 



N. mesotyla. — Smooth, narrowly linear laterally, slender on the 

 back, with a central spherical enlargement ; apices contracted, 

 obtuse. Length 1 -420th 



'^.ollonga. — Oblong-lanceolate and subacute, not produced (rostrate) 

 Salt water. Length 1 -720th. Mexico. 



N. oltma. — Small; oblong dorsally, and lanceolate; ends rounded, 

 obtuse. Kiitzing thinks it probably identical with N. afpendiculafa. 

 North Anicrica. 



