[Footnote I: The aborigines of South. America deemed it wonderful that the Europeans who first visited them should, without previous concert, agree in reading after the same manner the same scrap of manuscript, and in deriving the same piece of information from it. The writer experienced on this occasion a somewhat similar feeling. His specimens seemed written in a character cramp enough to suggest those doubts regarding original meaning which lead to various readings; but the geologist and the naturalist agreed in perusing them after exactly the same fashion--the one in London, the other in Neufchatel. Such instances give confidence in the findings of science. The decision of Mr. Murchison I subjoin in his own words--his numbers refer to various specimens of _Pterichthys_: "As to your fossils 1, 2, 3, we know nothing of them here, (London,) except that they remind me of the occipital fragments of some of the Caithness fishes. I do not conceive they can be referrible to any reptile; for, if not fishes, they more closely approach to crustaceans than to any other class. I conceive, however, that Agassiz will pronounce them to be fishes, which, together with the curious genus _Cephalaspis_ of the Old Red Sandstone, form the connecting links between crustaceans and fishes. Your specimens remind one in several respects of the _Cephalaspis_."] [Illustration: _PLATE I._] I have placed one of the specimens before me. Imagine the figure of a man rudely drawn in black on a gray ground, the head cut off at the shoulders, the arms spread at full, as in the attitude of swimming, the body rather long than otherwise, and narrowing from the chest downwards, one of the legs cut away at the hip-joint, and the other, as if to preserve the balance, placed directly under the centre of the figure, which it seems to support. Such, at a first glance, is the appearance of the fossil. The body was of very considerable depth, perhaps little less deep proportionally from back to breast than the body of the tortoise; the under part was flat; the upper rose towards the centre into a roof-like ridge; and both under and upper were covered with a strong armor of bony plates, which, resembling more the plates of the tortoise than those of the crustacean, received their accessions of growth at the edges or sutures. The plates on the under side are divided by two lines of suture, which run, the one longitudinally through the centre of the body, the other transversely, also through the centre; and they would cut one another at right angles, were there not a lozenge-shaped plate inserted at the point where they would otherwise meet. There are thus five plates on the lower or belly part of the animal. They are all thickly tubercled outside with wart-like prominences, (see Plate I., fig. 4;) the inner present appearances indicative of a bony structure. The plates on the upper side are more numerous and more difficult to describe, just as it would be difficult to