534 PROFESSOR GREGORY ON 
other localities. We have nothing for it, therefore, but to examine every speci- 
men of sea-bottom that we can procure. And the example of the Firth of Clyde 
is sufficient to prove that much remains to be done. 
It should also be stated here, that these Clyde dredgings are not exhausted. 
Indeed, it is a work both of much time and much labour fully to exhaust any 
such mixtures as these are. 
While these sheets are passing through the press, I am in a position to state, 
that I have already collected, from the same materials, so considerable a number 
of additional undescribed forms, that it will be necessary to describe and figure 
them in a supplementary memoir. Of these forms, a large proportion are discs, 
many of which are small, or only of a medium size; but there are also Naviculoid 
forms, Amphorze, and forms of a few other genera. 
I would further direct attention to the fact, that these dredgings differ ma- 
terially from each other, each being characterized by the prevalence of certain 
forms, although some forms are common to all. Thus, off Inveraray and Stra- 
chur, in Loch Fine, the proportion of large Campylodisci was very much greater 
in two gatherings than in all the rest, whether there or off Arran; while in 
Lamlash Bay, the material was remarkable for the great number and variety of 
Amphore, a character found in one only out of the seven dredgings from Loch 
Fine. This shows that the deposits may vary much in regard to species, and 
even genera, in localities at no great distance from each other, and points out the 
advisability of searching every corner. 
Lastly, it appears probable that some genera, whether such as have been 
adopted by Enrensere, Kurzinc, Bamey, and others, or entirely new, will have 
to be added to Professor Smiru’s list of British genera. This is especially the 
case with the numerous new filamentous forms, hardly any of which agree with the 
genera in the Synopsis. I have not for the present ventured to introduce any 
entirely new genus, but I have added Pyaidicula and Sceptroneis of EHRENBERG, 
and, more doubtfully, Diadesmis, also admitted, in a recent paper, by Professor 
Smite. I refrain from doing more; because I believe that genera established in 
the present imperfect state of our knowledge of species as well as of genera, are not 
likely to be permanent. In one case, I have pointed out the possibility of uniting 
in one genus and in one species three forms, Campylodiscus simulans, Surirella 
fastuosa, and Surirella lata, at present referred to two genera and three species. 
In distinguishing and describing the very numerous new forms figured in this 
communication, I have been careful to avoid unnecessary multiplication of 
species. In numerous cases I have united forms apparently distinct which a 
closer examination showed not to be so. And in every case where I have ad- 
mitted a new species, it has been because I could not reconcile it with any figures 
or descriptions which were accessible to me. I have also had the great advan- 
tage of frequent consultation with Dr GrevitLE, whose opinion has deservedly 
