234 
MARINE AND ESTUARINE DIATOMS. 
NITSCHIA. 
Nitschia. Frustules free, elongated, compressed. Valves linear, keeled, 
with one or more longitudinal lines of puncta. Keel frequently eccentric. 
N. scalaris E Sm. Passamaquoddy, Kennebecasis. (Plate II, Fig. 8). 
N. sigmoidea Ehr. Passamaquoddy, Kennebecasis. (Plate II, Fig. 5.) 
N. sigma W Sm. Passamaquoddy, Kennebecasis, (Plate II, Fig. 6.) 
N. bilobata. Passamaquoddy, Kennebecasis, (Plate II, Fig. 7.) 
N. closterium. Passamaquoddy, (Plate II, Fig. 9.) 
N. punctata Sm. Kennebecasis. 
N. Tryblionella H. Kennebecasis. 
N. circumsuta Bail. Kennebecasis. 
N. thermalis Ktz. Kennebecasis. 
N. angularis W S. Kennebecasis. 
N. longissima Ralfs. Kennebecasis. 
N. granulata Grun. Kennebecasis. 
N. paradoxa? Grun. Kennebecasis. 
N. constricta? Grun. Kennebecasis. 
N. littoralis Grun. Kennebecasis. 
N. levidensis Ant. Kennebecasis. 
ODONTIDIUM. 
Odontidium. Frustules quadrangular, united into *a filament. Valves 
elliptical or cruciform, with conspicuous costae. 
O. mutatile S. Kennebecasis. (Plate II, Fig. 37.) 
PLEUROSIGMA. 
Pleurosigma. Frustules simple, free, elongated, more or less boat-like. 
Valves sigmoid, with a central longitudinal line, which is also sigmoid,, 
and nodules at centre and extremities. Striae numerous and delicate 
arranged longitudinally, transversely or obliquely, and with very high 
powers resolvable into dots, which are frequently hexagonal. A very 
beautiful genus, embracing many species. 
PI. angulatun S. Passamaquoddy. (Plate II, Fig 13.) 
PI. balticum W S. Passamaquoddy. (Plate II, Fig. 11.) 
PI. strigilis S. Passamaquoddy. 
PI. fasciola E. Passamaquoddy. (Plate II, Fig. 12.) 
PI. strigosum S. Passamaquoddy. 
PI. aestuarii? Breb. Passamaquoddy. 
PI. formosum. Passamaquoddy. 
PI. Spenceri Grun. Passamaquoddy. 
