18 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



Amphitetras, Amphipentas, etc., are but varying forms of Triceratium and that this 

 is closely connected with Rhizosolenia. Whether Ditylium, as first described by the 

 writer should also be regarded as a related form, seems to him more doubtful — 

 Dr. Mann regards them as quite distinct. 



Plate II. Fig. 12. Skeletonema costatum — Grev. 



In the general form and structure of its frustules the species of this genus 

 closely resemble those of the genus Melosira — especially M. nummuloides or 

 M. varians; but differ in the much wider separation of the frustules and the presence 

 in the intervening space of numerous fine hair like processes, connecting the valves. 

 The chains thus formed are of considerable length and well adapted to flotation. 

 The specimens found were from Chamcook Bay and Deadman's Harbor, as well 

 as elsewhere about the Western Isles, and are not uncommon. The species found 

 by Dr. Ramsay Wright at Canso, are referred by him to S. costatum in reference 

 to the ribbed sides of the slender cylinders, and it is altogether probable that the 

 New Brunswick forms are of the same species. 



Plate II. Figs 13-14. Thalassiosira — Cleve. 



The genus Thalassiosira is very abundantly represented in the waters ad- 

 jacent to the New Brunswick coast about the entrance of the Bay of Fundy, es- 

 pecially in early summer, when they often form a considerable portion of the plank- 

 ton. Their generic identity is easily recognized by the somewhat wide separation 

 of the frustules and the fact that these are connected into chains solely by the agency 

 of a usually single fine thread, often of considerable length; and they probably 

 include several species, but, from the want of sufficient literature, the writer has 

 not in all cases been able to identify these with certainty. 



Fig. 13. Thalassiosira Nordenskioldii — Cleve. 



A form which is believed to be this species and which corresponds quite 

 closely to the latter as described and figured by Prof. H. H.. Gran (Nordisches 

 Plankton 1905) is very abundant in early June in the waters of the Western Isles, 

 being usually accompanied by Chaetoceros decipiens and Rhizosolenia. The 

 frustules are noticeable for their distinctly octagonal outline, from which at the 

 four external angles project minute spines, while the connecting filaments do not 

 usually exceed and are often less than the smaller diameter of the cell. The 

 chromatophores are somewhat variously disposed, but usually along the interior 

 of the cell wall, those of one side being connected with the other by a slight isthmus. 



Fig. 14. Thalassiosira. The distinctive feature of the form here represented 

 is the shape of the frustules, these being in the form of lengthened cylinders, which 

 are connected into chains by threads arising from the centres of their opposite 

 circular ends. The chromatophores, which are minute and granular, are con- 

 densed at the same points. No external processes were observed. 



