NEW FORMS OF MARINE DIATOMACE-E. 481 



Fine dredging, with N. Clavkulus, N. Musca, &c. I 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. PI. IX., fig. 10. Form elliptic-lanceolate, very 

 broad; ends subacute or acute. Length from 0-003" to 0-005"; breadth from 

 00023" to 00032". 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. Striae 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 N. Lyra, Ehr., and also to N. 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 N. Hennedyi, while the broad blank spaces distinguish it from 

 N. Lyra, in which, as we shall see, these spaces are linear. Besides this, N. Lyra 

 very often occurs with produced ends, and never has the peculiar form of N. 

 spectabilis. The latter never occurs with produced ends. Moreover, under a low 

 power, N. spectabilis has a bright brown colour, in the striated parts, not observed 

 in N. 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 prcetexta= Pinnularia prcetexta, Ehr. PI. IX., fig. 11. Form a 

 pure and broad oval. Length from 0004'' 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 striae. At the margin of the valve is a rather 

 broad band of striae, exactly like those of the central bands. This marginal band 

 is of uniform width till near the apices, where it gradually becomes narrow. 

 Striae 8 to 10 in 0-001". The broad intermediate space between the marginal and 

 central bands is not blank, as in N. Hennedyi, but is irregularly dotted or stippled 

 with round granules, precisely the same as those of the striae 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 striae. 



This conspicuous and beautiful species has been figured by Ehkenberg, as 



VOL. XXI. PART IV. 6 O 



