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, Amphorae, 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 

 Amphorae, 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 Ehrenberg, Kutzing, Bailey, and others, or entirely new, will have 

 to be added to Professor Smith'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 Pyxidicula and Sceptroneis of Ehrenberg, 

 and, more doubtfully, Diadesmis, also admitted, in a recent paper, by Professor 

 Smith. 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 simidans, 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 Greville, whose opinion has deservedly 



