No. 2.] GEOLOGY AND MINERALOGY. 227 



GEOLOGY AND MINERALOGY. 



On the Canadian Trilobite with Legs. — The followins: 

 is an extract from the Report of the Committee of the British 

 Association on the Structure and Chissification of the Fossil 

 Crustacea, at the Edinbur<>-h meetino-, August, 1871. The com- 

 mittee consists of Henry Woodward, F.G.S., F Z.S., Dr. Duncan, 

 F.R.8., and R. Etheridge, F.R.S. The report was drawn up by 

 Mr. Woodward. 



''Since noticing the occurrence of an Isopod (Pakega CarterV)^ 

 from the Kentish, Cambridge, and Bedford Chalk, Dr. Ferd. 

 Roemer, of Breslau, has forwarded me the cast of a specimen of 

 the same Crustacean from the Chalk of LTpper Silesia. This, 

 together with the example from the Miocene of Turin, gives a 

 very wide geographical as well as chronological range to this 

 genus. 



A still more remarkable extension of the Isopoda in time is 

 caused by the discovery of the form which I have named Proearc- 

 turus in the Devonian of Herefordshire, apparently the remains of 

 a gigantic Isopod resembling the modern Arcturus Baffinsii. 



I have also described from the Lower Ludlow a form which I 

 have referred with some doubt to the Amphipoda, under the oene- 

 ric name of Necrogamynarus. 



Representatives both of the Isopoda and Amphipoda will doubt- 

 less be found in numbers in our Palaeozoic rocks, seeing that 

 Macrouran Decapods are found as far back as the Coal-measures * 

 and Brachyurous forms in the Oolites. f 



* Indeed the suggestion made by Mr. Billings as to the Trilobita 

 being furnished with legs (see Quart. Journ. Geol Soc, vol. xxvi., 

 pi. 21, fig. 1), if established upon further evidence, so as to be 

 applied to the whole class, would carry the Isopodous type back in 

 time to our earliest Cambrian rocks. 



I propose to carry out an investigation of this group for the 

 purpose of confirming Mr. Billings's and my own observations, by 

 the examination of a longer series of specimens than have hitherto 



* Anthrapalsemon Grossartii, Salter, Coal-measurevS, Glasgow, 

 t Palseinachus longipes, H. Woodw., Forest Marble, Wilts. 



