NEW FORMS OF MARINE DIATOMACE^. 527 



giving to the detached segment a very peculiar character. The segments are 

 marked by strong, coarse strise, about 20 in 0001 ". In one focus (fig. 97) the 

 segments are well seen in the frustule ; in another, fig. 97 b, the frustule is seen 

 to consist of 9 or 10 convergent bars, which are coarsely granulate. In fig. 97 

 the lateral segments are seen to be nearly in apposition, with a narrow space 

 between them, of varying width, from the undulations of the ventral margin. 

 The inner line of each lateral segment is very slightly curved ; the nodule lies 

 nearest to the ventral margin. The detached segments, figs. 97 c, and 97 d, are 

 precisely like Cymbellze, and for a long time I considered them as such, with those 

 of A. granulata and A. cymbifera. But the view in fig. 97 showed the real 

 nature of these forms. Want of space alone prevents me from giving figures of the 

 entire frustule corresponding to the segment in fig. 97 d. The reader is requested 

 to compare fig. 97 with the corresponding view of A. Grevilliana, fig. 89. 



This very striking species occurs only in the stony Loch Fine dredging, so often 

 alluded to, where it is rather frequent, both entire and in detached segments. 



99. Amphora costata, Sm. PL XIV., fig. 99. This species is described b} T 

 Professor Smith in his Synopsis, vol. L, where the entire frustule, and also a half 

 frustule, are figured. But little is said of its peculiar structure, and the detached 

 segment is not figured. For this reason, and to show the analogy between this 

 species and the three preceding ones, I have figured a detached segment (fig. 99). 

 Form of segment highly arcuate, very broad in the middle. Ventral margin 

 straight, or slightly concave, but often, as in the example figured, which is a 

 rather small one, with a rounded prominence in the middle close to the nodule. 

 The ends are capitate. Striae coarse, conspicuous, about 14 or 16 in 000V. 

 thicker and stronger near the dorsal margin. Length from 0-002" to 0-0033" ; 

 breadth in the middle 0-0012" to 0-0016". 



It will be seen that in this species also the segment resembles a Cymbelln, 

 although it is a very broad and highly arcuate one. When the segments are 

 united, as in the entire frustule, it is not easy to see their real characters. The 

 backs of these segments, or longitudinal bars, are, as in Professor Smith's accu- 

 rate figures, marked by very coarse distant granules, which give no indication of 

 the peculiar striation of the detached segments. Hence it was very long before 

 I was able to detect the component parts of the frustule when detached, or to re- 

 fer the form shown in fig. 99 to A. costata. But some specimens, as in the pre- 

 ceding species, when carefully focussed, clearly show their true nature. 



100. Amphora bacittaris, n. sp. PI. XIV., figs. 100 and 100 b. Form of frustule 

 linear, narrow, with somewhat rounded ends, which are subacute. Length about 

 0-0017"; breadth about - 0003". In one focus it exhibits two lateral portions se- 

 parated by a middle space, the sides of which are perfectly straight, the ends 

 beautifully rounded. In another, the whole frustule is seen to be composed of 

 very narrow bars, separated by very sharp lines, converging on the ends, and 



