D uring a visit to the south of Scotland last autumn I collected some fossils from the older rocks of that district, which appear interesting as adding another link to the chain of evidence by which the true age of these deposits may he ascertained. Taken in connection with the fossils formerly noticed* and with those procured by Mr. Moore in Wigtonshire†, they may be regarded as rendering the Lower Silurian age of one part of these beds almost certain, so that the connection of the rocks and mountain-chains of this portion of Britain with those of other countries may now be so far traced out. The fossils which Mr. Salter last year kindly determined were chiefly procured from the only bed of limestone known in the Silurian rocks of the south-east of Scotland. My hopes of obtaining better or more characteristic specimens from that locality were disappointed, and not even a single new form was discovered after a careful search. Indeed, the highly crystalline texture of the limestone, probably occasioned by a mass of trap with which it is always associated, renders it very improbable that this bed will ever add much to our knowledge of the beings existing in the seas in which it was deposited. My researches in the slate rocks were more successful, especially in the Grieston quarry near Traquair. In this place the rocks consist of clay-slate, sometimes passing into a fine greywacke, and are wrought for a coarse kind of roofing-slate. The strata are thin