126 



have named it S. vitra^, with the charateristics of which I am only 

 acquainted from the short description in Pritchard, bpcause Professor 

 Bailey gives the S. vitra? as the only species found in Southern waters. 

 Otherwise I might have designated it by S. lanecolata. 



Synedra amphirhynchus (?) E., Amite river. Only distinguished 

 from the preceding in having the front view perfectly linear, with 

 truncate but not dilated ends. The form of the valves is nearly the 

 same as that of the preceding species, but it has no quadrangular 

 median space. It is probable that neither of the above designations 

 of Synedra are the proper ones. My object was to include them in 

 the list by some specific name, the character of which they approxi- 

 mate. 



Synedra lunaris, E., Amite river. A great number of Synedras are 

 still undetermined. 



Cymatopleura elliptica (?), Breb., Grand Isle. We have but a 

 single specimen in side view. 



Surirella splendida, Ehr., (we have specimens of the large and 

 stunted variety) Rapides and Baton Rouge. 



Surirella Craticula, Ehr., Lake Pontchartrain. 



Surirella striatula, Turp., Lake Pontchartrain. 



Surirella ovata (?) Ehr., Baton Rouge. 



Surirella biseriata, Breb., Rapides. 



Striatellie^:. 

 Tabellaria fenestrata, K., Rapides. 



Melosire^:. 



Melosira nummuloides, Ag., Grand Isle. 



Melosira Jurgensii (?), Ag., Grand Isle. 



Melosira varians (?), Ag., (In filaments of great length) Baton 

 Rouge. 



Pixidicula compressa, Bail, Grand Isle. This is one of the most 

 beautiful diatoms of the collection. Its dotted lines reflect the light 

 in a variety of colors. 



Coscinodisce^:. 

 Coscinodiscus radiatus ? Ehr., (many specimens,) Grand Isle. 



The specimens are comparatively small, the punctac are cellulose, 

 smaller in the margin, and the radiated lines are obscure; but the 

 punctac are all distinct and very large. 



