486 PROFESSOR GREGORY ON 



in vol. i. (fig. 152 a*) given as N. elliptica, which is not lyrate; but the name 

 given by Ehrenbeeg proves that he regarded the lyrate character as a principal 

 one. I have therefore figured it, in order to show that it occurs in Britain as 

 Ehrenberg described it. 



14. Navicula Lyra, Ehr., var. /3, alrupta. PI. IX., figs. 14 and 14 b. Form 

 usually oval, more or less elongated ; sometimes linear in the middle, broad, with 

 parallel sides, and obtusely acuminate at the extremities. I have hardly ever seen 

 it with contracted and produced ends, as is so often observed in N. Lyra. Size and 

 striation as in N. Lyra, but the blank spaces, which are linear, as in that species, 

 instead of being recurved at the ends, or lyrate, bend inwards at the ends, so as 

 to form two narrow ellipses meeting in the central nodule. These linear blanks 

 in this variety stop abruptly at some distance from the terminal margin of 

 the valve, which, in N. Lyra, they often, though not always, reach. 



This form, which is frequent in the Glenshira sand, as well as in the dredg- 

 ings, is that already referred to as having been figured in vol. i. of the Synopsis 

 (fig. 152 a*), as N. elliptica, and since referred to as N. Lyra, in vol. ii. 



I figure it here, both that it may be compared with the N. Lyra of Ehrenberg, 

 and that it may be contrasted with N. spectabilis (fig. 10), which is supposed by 

 some to be a form of N. Lyra. The form of the latter, and the fact that the 

 blank spaces in it are not linear, but broad, and reach the margin, all which cha- 

 racters are very constant ; to which may be added the rich brown colour of N. 

 spectabilis in balsam, under a low power, seem to me to be sufficient to distinguish 

 it from N. Lyra. The reader is requested to compare fig. 10 with figs. 13, 13 &, 

 14, and 14 b. The latter forms are colourless in balsam. 



15. Navicula Smithii, var. (3,fusca. PI. IX., fig. 15. Form an elongated oval, 

 broad, with rounded ends. Length from 0003" to 00063", and even more ; 

 greatest breadth from 00014" to 00028". Median line narrow at the terminal 

 nodules, which are a little within the apices ; broad, and formed of three parts, 

 all ending in expansions, on each side of the central nodule. Nodule large, broad, 

 indefinite. Striation very coarse, and coarsely moniliform, not reaching the me- 

 dian line, but leaving on each side of it a narrow blank line, terminating in the 

 angles of the nodular blank. The whole spaces, taken together, form two very 

 acute long triangles, base to base Striae about 10 in 0001". At about one-third 

 of the distance from the median blank lines to the margin, the striae are traversed 

 by a strong, dark line, which is often, as in the figure, nearly rhombic, but is 

 generally curved, though very slightly. This line is caused by a ridge or eleva- 

 tion of the valve, and is very conspicuous. Valve thick, and highly convex, of a 

 strong brown colour, in balsam, under the \ or f of an inch objectives. 



This form, which is very conspicuous, occurs, like the two preceding, both in 

 the Glenshira sand and in the dredgings ; and in that of Professor Allman from 

 Lamlash Bay and one from Loch Fine, it is frequent. I give it as a variety of N. 



