166 



Syeingiditjm simplex, Bail., nov. sp. 



Frustiiles minute, punctated ; central portion quadrangular, larger 

 and stouter than in S. Americanum. Valves unequal, hoth gradually 

 tapering into p}Tamidal cones, one of which terminates in a mucro, 

 the other in a minute sharp spine. Valves nearly symmetrical. Ko 

 basal processes as in S. Americanum. 



Hab. Para River. 



NiTSCHIA OBLONGA, L. W. B., nov. sp. 



Small, linear-oblong, with sub-acute apices ; valves a little narrower 

 at the middle than at the ends, but with no central constriction. 

 Marginal puncta small, and close. Surface minutely punctate in 

 transverse parallel stria. 



Hab. Para River. 



Several other forms believed to be new, will be hereafter described 

 in connection with the plates. The following list includes all the 

 forms yet observed in the Para and Amazon. 



li8t of dlatomace^, collected during the cruise of the 

 United States Brig Dolphin, in the Para and Amazon. 



Achnanthes. 

 Actinocyclus. 



Actinoptychus senarius, Ehr. 

 Actinoptychus denarius, Ehr. 

 " 13 rays. 



*Amphitetras cuspidata. Bail. 

 Amphora ovalis, K. 



* " delphina, L. W. B. 

 Biddulphia Baileyii ? Sm. 



" tridentata, Ehr. 



* " tenuis. Bail. 

 Cerataulus turgidus, Ehr. 

 Coscinodiscus eccentricus, Ehr. 



" gigas, Ehr. 



" lineatus, Ehr. 



" oculus-iridis, Ehr. 



" subtilis, Ehr. 



* " ? tenuis. Bail. 

 Dicladia Capreolus ? Ehr. 



* " mamillana, B. 

 Dictyocha fibula, Ehr. 

 Diploneis, 

 Discoplea Klitzingii, B. 



. . =Cyclotella Kiitzingiana, Sm. 



*Ditylimi trigonum. Bail. 



* " inasquale, B. 

 " (not named). 



Eunotia dizyga ? Ehr. 



* " (with unequal teeth). 

 Eupodiscus nov. sp ? 



Allied to E. radiatus. 

 *Fragillaria constricta ? Ehr. 

 *Gomphonema sphasosphorum ? , 

 Ehr. 



Grammatophora, ? 



Hyalodiscus, 

 *Lithodesmium contractum. Bail. 

 Melosira sulcata. 



* " granulata, L. W. B. 

 Navicula Bacillum ? Ehr. 



" Baltica, E. S. 



« Lyra, E. 



" lineolata ? Ehr. 



* " septenaria, B. 

 " viridis ? Ehr. 



*Nitschia oblonga, L. W. B. 

 " mesolepta, B. 

 = N. linearis ? Sm. 



