Naviculacea.'] infusorial animalcules. 479 



Synedra valens.-^Yerj large, widely linear, minutely pinnate, ends 

 truncate (P. 15., f. 44).; a.])'pvoa.ches JEchinella ful^ens. Fresh 

 water. Mexico and New York. 



S. incurva. — Linear, but flexuose, smooth, and very narrow, with 

 four equal sides (if rounded). Length 1-28 8th. The apparent 

 double margin may indicate the canal of a Spongolithis. If a 

 Spongolitliis ? (a genus of PhytoHtharia). Bermuda. 



S. hngiceps. — In form approaches nearly S. capitatum, but has its 

 ends elongated and styliform. Length 1- 12th to l-144th. Living 

 in Lake Michigan. 



S. spectalilis. — Large, widely linear, with one apex cuneate trun- 

 cate, the other rounded. Chili, Mexico, United States, Bosphorus, &c. 



8. sigmoidea. — A New Holland species, discovered by Ehrenberg. 



S. quadraiiguktris (Kiitz), very small ; on one side very narrowly 

 linear, on the other wide, and sub-obliquely quadrangular. Length 

 1 -2880th. On Conferva. Coast of Norway. 



S. (}) minutissma. — Very minute j on one side narrowly linear, on 

 the other {dorsum, Ehr.) lanceolate and rather obtuse. Length 

 1 -2400th. On the shore at Eerrara, on Oscillatoria. 



S. perpusilla. — Yery small ; narrowly linear laterally, dorsaUy 

 lanceolate and contracted near the obtuse ends. Length 1 -2400th. 

 Yenice. 



S. biasolettiana. — Yery smaU ; laterally narrowly linear and curved ; 

 dorsally obtusely lanceolate. Length 1 -2640th. On Oscillatoria 

 at Trieste. 



S. Pusilla. — Small ; laterally widely linear, dorsally oblong, elliptic, 

 with obtusely rounded apices. Length 1-1 800th. On Oscillatoria, 

 Carlsbad. 



S. Frustuluni. — Small, linear; laterally truncate; dorsally cun- 

 eate, acute; imbedded in a gelatinous mass. Length 1-1 320th. It 

 forms a green stratum on rocks in Italy. 



S. Palea. — Small ; laterally, narrowly linear ; dorsally -wdder, but 

 narrowly lanceolate and acute. Length l-650th. On Oscillatoria, 

 Trieste, &c. 



S. acicularis. — Small laterally, very narrowly Unear; dorsally 

 lanceolate, much prolonged (acuminate). Length 1 -350th. 



S. angiistata. — Laterally narrowly linear ; dorsaUy wider, oblong, 



