220 PROCEEDINGS OF THE 



appears to be the structure in CamjnjIocUscus, and the two genera 

 might ahnost be united, as proposed by Dr Gregory, did not we 

 find the two extremities and axis of the upper valve in Snrirella, 

 placed directly over those of the lower valve, while in Campylo- 

 discus, the axis of the one valve is at right angles to that of the 

 other. C. bicniciatus of Gregory (Micr. Journ., V., Trans, tab. 5, f. 

 42) exhibits both valves combined, the poles of the one at right 

 angles to those of the -other, while his C. simulans (fig. 43) is a 

 single valve of the same species, which does not difi"er essentially 

 from C. parvuhis Sm. 



From Surirella must certainly be removed S. cmticula, although it 

 is not easy to point out what its real affinities are. In the Micr. 

 Journal, VIII., Trans., p. 138, Dr G. C. WaUich considers it a 

 monstrosity, and that it was more allied to Pimiularia than 

 to Surirella. He had occasionally seen the striation of Navkula on 

 it, as well as the " canaliculate structure of Surirella." This I 

 have also seen : whenever the naviculoid striation occurs, there is 

 a central nodule. In one sample from a peat deposit at Marton 

 (near Skirlaugh, a few miles from Hull), the form with costse 

 only was not scarce, and was accompanied by a few valves pro- 

 vided with both costae and the horizontal striation ; in the same 

 were Navicula hirostrata of Gregory, N. cusjndata, and N. amUgua. 

 AU the three, and likewise S. craticula, have precisely the same 

 peculiar kind of nodule, which is considerably different from what 

 we usually see in Navicula. N. cuspidata and N. ambigua only 

 differ slightly from each other by the form of the valves, and are 

 certainly the same species. They have parallel striae; but in 

 N. hirostrata the valves are slightly more narrow, and the striation 

 is radiating and coarser at the middle. The S. craticxda agrees in 

 size and shape mth many valves of N. hirostrata; but the stria? 

 are scarcely so radiating, at least in the few valves I have seen 

 with them. Mr G. Norman, of Hull, in his account of the 

 diatoms found near Hull, assigns to it radiating strise, and, as he 



DowTa, and to the lake in County Antrim. It is probable that the Countess had 

 obtained both when in Belfast. The true Lough Moume deposit has of late 

 been called by some in London, Avho prepare sUdes for sale, the Bellahill 

 deposit, while that again is called by them the Carrickfergus deposit. A 

 deposit is also got at Lough Mounie, in the County of Donegal, remarkable for 

 containing Nav. Trochus Ehr. (perhaps a vainety of N. serlans), sparingly — a 

 diatom also found at Loch Oich, a part of the Caledonian Canal. 



