127 



Coscinodiseus subtilis ? Ehr. Punctiform in radiating triangular 

 linear rays. Grand Isle. 



Aetinoptychus undulatus, Khr., (one single specimen,) Grand Isle. 



Bidulphie.e. 



Bidulphia obtusa, Kich, (only one specimen,) Grand Isle. [Cor- 

 responds precisely with the description and figure of Fritchard.] 

 Odentella polymorpha, Rab., (A great number of specimens,) 



(J rand Isle. 



Terpsinoeje. 



Terpsinoe mnsica, Ehr., (A great number of specimens,) Grand 

 Isle. 



CoCCONEIDE.E. 



Cocconeis Pediculus ? E., (Found collected in great numbers,) 

 Lake Pontchartrain. 



This species resembles C. placentula, but it is smaller, and has 

 no transverse stria\ The longitudinal strue are undulating, from 

 three to four on each side of the median line. In most of the spe- 

 cimens the stria? are obscure. They are congregated in large 

 numbers, on Enteromorpha. 



Cocconeis Finnica, E., (This is a very beautiful species of Cocco- 

 neis,) Lake Pontchartrain. 



This Cocconeis corresponds with Ehrenberg's figure; it has 

 transverse stria?, and a lanceolate longitudinal fascia bisected by 

 median line and nodule. 



We have many other specimens of Cocconeis, but they are unde- 

 termined. 



ACHNANTHE^. 



Achnanthes subsessilis ('?), K. — (numerous specimens) — Grand 

 Isle. Some of these specimens are very beautiful. 



CYMBELILE. 



Cymbella Ehrenbergii, K.( — numerous specimens) — Baton Rouge. 

 There are two varieties of this species, one broad lanceolate in 

 navicular form, and the other small and rounded, with slightly pro- 

 duced rostrate apices. Both varieties are distinctly striated. 



Cymbella maculata, K., Baton Rouge. There are several other 

 species of cyinbella} not determined. 



