16 



PROCEEDINGS OF THE ACADEMY OP 



I add a list of the ordinary grouping of species in these localities. This is 

 necessarily incomplete and liable to error, owing to the fact that in some of 

 these muds, within the immediate influence of mountain streams, as parts of 

 the Saco spring the Flume Bethel there is a large dilution with more modern 

 forms. These I have excluded and placed in a list by themselves. The 

 absence of these species in the still pond localities of the White Mountains, is, 

 I think, sufficient evidence of their extraneous habitat, when found along with 

 the grouping below. 



Cymbclla cuspidata, C. helvetica, Epilhemia ventricosa, E. argus, Eunotia robusta, 

 Eu. incisa, Surirella nobilis, S. oblonga, S. decora, Navicula firma, N. serians, N. 

 rhomboides, N. major, N. tabellaria, N. viridis, N. acrospheria, N. radiosa, N. 

 mesolepta, N. borealis, iV. Staureiformis, N. elliptica, JV. cuspidata, Stauroneis 

 phenicenteron, St. gracilis, St. Baileyi, St. anceps, St. legumen, Cocconema lanceolatum, 

 G. cymbiforme, Gomphonema coronalum, G. turgidum, (var. G. capitatum) ? 

 Gomphonema, (var. G. acuminatum), Himantidium areas, IT. pectinate, Odontidium 

 tabellaria, Fragillaria, (doubtful?) Achnanthidium ? Tetracyclic lacuslris, (rare). 

 Diatoma elongatum, (rare), Tabellaria vulgaris and vars. Orlhosira orichalcea, 

 Cocconeis Thivaitesii, (rare), Nitzschia spectabilis, (rare), Synedra ulna, (rare), 

 Navicula=Amphiprora navicular is, (Ehr.)? (common in sub-peat and peat), 

 Navicula scutelloides, (rare). 



The following are, probably, extraneous species : Odontidium mesodon, 0. 

 mutabile, Meridion circulare, Cocconeis placentula, Synedra radians, Nitzchla am- 

 phioxys, N. tenuis, Pleurosigma Spencerii, Gomphonema capitatum, G. geminatum, 

 Asterionella formosa, Colletonema vulgar e. 



Denticula and Amphiprora are not represented in any of these deposits, 

 unless by one or two doubtful forms, one of which is figured in (pi. i., fig. 6), 

 Amp. ornata, the only fresh water species, is not common so far north. 



*(I have omitted to notice an abnormal variety of Surirella decora t in 'the Wolfboro mud. 

 This is ovate; the median line extending for little more than one half the length of the valve, 

 leaving an equal open area at either end. From the extremities of the median line, the faint 

 costse branch out with a beautifully radiant arrangement, appearing as if they all arose from the 

 same point. I have found this form also at Montmorency Falls, Canada.) 



[Jan. 



