NEW FORMS OF MARINE DIATOMACEZ. 481 
Fine dredging, with V. Claviculus, N. Musca, &c. 1 have also seen it, though 
much more sparingly, in some of the other dredgings, both from Loch Fine and 
Lamlash Bay. 
10. Navicula spectabilis,n. sp. Pl. IX., fig. 10. Form elliptic-lanceolate, very 
broad; ends subacute or acute. Length from 0:003” to 0:005”; breadth from 
00023” to 0:0032”. Median line sharp, having close to it on each side a narrow 
striated band, interrupted at the middle. Central nodule large, indefinite. There 
is a marginal band of striation, which is very broad in the middle, where it pro- 
jects inwards to an obtuse point, and very narrow at the apices. Strize coarse, 
moniliform, about 22 in 0:001".. The blank spaces between the marginal and 
central bands are very broad; and this part of the valve is so thick and strong, 
that in fractured specimens we never find it broken across, but we often see the 
entire blanks, united by the central nodule, which is elongated laterally, separated 
from all the striated parts, forming a singular object. 
This form is allied to V. Lyra, Ehr., and also to V. Hennedyi. I consider it, 
however, quite distinct from either. It occurs frequently in Lamlash Bay; but I 
have not yet seen it elsewhere. The form and width of the marginal band dis- 
tinguish it from VV. Hennedyi, while the broad blank spaces distinguish it from 
WN. Lyra, in which, as we shall see, these spaces are linear. Besides this, V. Lyra 
very often occurs with produced ends, and never has the peculiar form of WN. 
spectabilis. The latter never occurs with produced ends. Moreover, under a low 
power, J. spectabilis has a bright brown colour, in the striated parts, not observed 
in NV. Lyra. Lastly, I find this form remarkably uniform and constant in its 
characters. It is very conspicuous, and generally larger than N. Lyra. 
11. Navicula pretecta=Pinnularia pretexta, Ehr. Pl. 1X., fig. 11. Form a 
pure and broad oval. Length from 0-004’ to 0°005”; breadth 0-0025” to 0-003". 
Median line sharp, the central extremities ending in large, rounded expansions, 
which are bent to the same side. Central nodule indefinite, extending trans- 
versely. On each side of, and close to the median line, a narrow linear band of 
_ very coarse and coarsely moniliform striz. At the margin of the valve is a rather 
broad band of striz, exactly like those of the central bands. This marginal band 
is of uniform width till near the apices, where it gradually becomes narrow. 
Strize 8 to 10 in 0-001". The broad intermediate space between the marginal and 
central bands is not blank, as in V. Hennedyi, but is irregularly dotted or stippled 
with round granules, precisely the same as those of the striz. Towards the centre, 
and near the ends, the median striated bands pass gradually into the sparsely 
dotted space. Between these points the median bands end more abruptly. The 
scattered granules are consequently most thickly set round the nodule and near 
the apices. The granules are so large, that there are not more than five in each 
of the longest of the marginal strize. 
This conspicuous and beautiful species has been figured by EHRENBERG, as 
VOL. XXI. PART Iv, 60 
