Vol. 52.] ANNIVERSARY ADDRESS OE THE PRESIDENT. Xoi 



Life-history oe the Crustacea in Later Palaeozoic 

 and in Neozoic Times. 



In my Address, in February last year, I endeavoured to set 

 before you as briefly as possible, an epitome of the more interesting 

 points in the earlier chapters of the life-history of the Crustacea — 

 a Class so ancient as to entitle it to take precedence over the whole 

 of the Yertebrata, and probably over half the Invertebrata also, in 

 the geological record. 



Prom Lower Cambrian times to Carboniferous we showed that 

 the Crustacea were mainly represented by the great and numerous 

 order of the Trilobites, while bivalved Ostracods, huge Pod-shrimps 

 (Phyllocarida) and giant Merostomata, such as Eurypterus and 

 Pterygotus, with a few small King-crabs, fill up the picture of 

 marine crustacean life. 



To whatever part of the world we direct our gaze over the Palaeo- 

 zoic seas, the same group of organisms is more or less abundantly 

 represented ; — indeed it may be said that, until we reach the Upper 

 Silurian, the Trilobites almost entirely occupy the primaeval waters 

 to the exclusion of other crustacean life. But from this stage up- 

 wards the Trilobites are more restricted, while the large Pod-shrimps, 

 Ceratiocaris, appear in numbers, together with the gigantic Ptery- 

 gotus, the latter attaining its maximum in the Old Red of Scotland. 



Some 8 or 9 genera of Trilobites still continue on in the Devo- 

 nian and the Carboniferous Limestone, in the latter formation 

 reduced to about four genera, after which they disappear entirely. 



Whether the Trilobites continued to live on in some of those 

 marine areas which probably existed adjacent to the larger fresh- 

 water and estuarine ones, amidst which the great subaerial growths 

 of the Coal-period were being accumulated, we do not certainly 

 know, but in the succeeding Permian epoch they have left no 

 evidence behind. 



As we scan the record of these old Carboniferous rocks, so rich in 

 organic remains, we seem to stand on some lofty beacon-hill, whence 

 we can cast our glance upwards and downwards along the stream 

 of time. Beneath our feet lie buried the last representatives of 

 those aboriginal races now quite extinct, the Trilobita and the 

 Eurypterida, whose ancient hosts peopled the seas of Devonian and 

 Silurian ages and some of whose predecessors reached far away 

 to the Lower Cambrian epoch. Beside them lie the earliest repre- 

 sentatives known of our modern Decapoda, Stomatopoda, and Isopoda, 

 then but a few and feeble folk, but now the dominant races of the 



