OF BRITISH FRESH-WATER DIATOMACE^. 1 3 



42 Gomphonema Sarcophagus, W. G. — This species occurs 

 abundantly in the Lochleven gatherings, but it occurs also 

 in several gatherings made near Edinburgh, and in others 

 from Fife, Stirlingshire, Lanarkshire, and elsewhere. Indeed 

 it would seem not to be uncommon. In form it is linear, 

 rather narrow, the sides gently curved, so as to form a sort of 

 shoulder at the widest part, after which it contracts a little, 

 and again expands to a somewhat truncate extremity. The 

 opposite end is nanower, and, with the exception of a trifling 

 expansion at the apex, becomes continuously narrower. These 

 things give to it very nearly the sliape of a coffin. The F. V. 

 is, as usual in this genus, cuneate. Length about 0014 inch. 

 Striae 20 to 22 in -OOl". 



I have now only to add a few words on the distribution of 

 the Diatomacea in our fresh waters. I have not only found, 

 as Ehrenberg has done, that a large number of species occur 

 in every locality, but even in tlie case of the forms just 

 described, which, from their having been overlooked, might 

 be supposed to be very raie, most of them have been observed 

 in more than one, frequently in several different and distant 

 stations. 



It must not be supposed that the gatherings which I have 

 examined are exhausted. Tlie fact is, that only a small 

 number of them, no doubt the most interesting and the most 

 promising, have been at all minutely explored, and I would 

 particularly direct attention to the fact, that with the exception 

 of only two or three species, all the forms now figured are 

 actually to be found in four gatherings, those, namely, of 

 which I have spoken as Elchies, Elgin, Lochleven, and Dud- 

 dingston Loch. Several of these forms were first observed in 

 other gatherings, tliough not many, but in time they have all 

 been found in these four. Nay, the Lochleven gathering 

 alone has been found to yield nearly the whole of them. If, 

 therefore, I had been confined to these four gatherings alone, 

 I should have detected, by careful exploration, all the forms 

 now figured as new. This shows what I formerly alluded to, 

 the importance of minute examination, without which many 

 interesting forms are daily overlooked. It is no argument 

 against this to say that species cannot well be ascertained 

 from a few scattered specimens, for what is rare and scattered 

 to-day, may be found in abundance to-morrow. Thus the 

 doubtful St.auroneis which I have figured occurs very sparingly 

 in the Lochleven gathering. Had it never occurred but there, 

 its character could have been easily ascertained. But in the 

 Findhorn gatherings it occurs abundantly. Stauroneis obliqua 

 occurs, at present, only in Lochleven, and that sparingly ; but 



