16 NAVICULER, 
this species are those given above, It is somewhat remark- 
able that it has been described as constituting three dif- 
ferent species. The late Prof. Smith’s description and 
figure of N. tumens, Sm., give a very inadequate idea of 
the arrangement of the strie in this curious form; the 
peculiar arrangement is not easily observed, except with 
superior object-glasses and suitable illumination. I have 
carefully compared British specimens of this species with 
those of N. rostrata, Ehren., occurring in the Bergmehl of 
Santa Fiore, and with those of N. sculpta, Ehren., found 
in the fossil deposit from Franzensbad, and figured in the 
‘ Mikrogeologie ;’ and I find them to be perfectly identical. 
The British and Santa-Fiore specimens are exactly alike, 
while those of N. sclupta from Franzensbad are larger 
and have the granular structure of the valve and the 
peculiar arrangement of the strie much more strongly 
developed, so as to be distinctly visible even with a mode- 
rately low power. To this circumstance, and the imperfect 
instrument employed in 1840, in the description of N. ros- 
trata, we may, perhaps, attribute the fact of Ehrenberg 
having described it as constituting two distinct species. 
Prof. Smith appears to have been unacquainted with N. 
rostrata. 
Hab. Brackish water, Newhaven, Sussex (Prof. Smith) ; 
near Hull (Mr. Norman) ; near Liverpool (Mr. Comber) ; 
Salt Marsh, Warkworth, Northumberland (A. S. D.). 
