359
States on the other. They thus form in the general historyof the globe a connecting link between deposits considerablymore than four thousand miles apart I may add that, dur-ing the last few years, I have been able to place in my littlemuseum, beside its Silurian fossils of America and England,a not less ample collection of the Silurian fossils of our owncountry, which, though still inadequate, contains several rareorganisms, with which, so far as is yet known, the English deposits could not have supplied me. Still, however, muchremains to be done in this curious field. I was shown onlya few weeks ago, by a gentleman from the neighbourhood ofLesmahagow, a fossil crustacean, derived, he said, from theGrauwacke of that neighbourhood, which, so far as I couldjudge, in its rather indifferent state of preservation, is newto Scotland , and which very considerably resembles that Hy-menocaris of North Wales which Sir Roderick describes inhis “ Siluria” as a true primordial fossil. And where the crus-tacean occurs, it is more than probable that other organismswill yet be found.
The Lower Old Red Sandstone of Scotland has been morethoroughly wrought out than perhaps any of the other for-mations of the country, and it occupies, in consequence, alarger space in my collection. I have not yet found fossils inthe Great Conglomerate, which forms its base ; nor perhapscould organisms, save of the most robust structure, be ex-pected in a rock formed of great water-rolled pebbles, which,ere they could have assumed their present rounded forms,must have been tossed by the storms of ages. In the pebblesthemselves, however, we have curious glimpses afforded usof the old metamorphic rocks of Scotland ; which were, wefind, considerably different in the group from the rocks ofsimilar origin that in the present age of the world composeour great Highland nucleus. The schistose gneisses, nowthe prevailing metamorphic rocks of the kingdom,—for they