The paper of Dr. A. Kunth, “Ueber Pteraspis,” Zeitschr. der Deutscheri Geol. Gesellsch., 1872, Hft. 1, came into my hands at a time when I had just been examining the specimen of which a restored figure is given in the Plate accompanying this paper. I took an early opportunity of replying to Dr. Kunth's adventurous assertions in the Academy, and the remarks then made have been reproduced in, this Journal (April, 1873). I need, therefore, here, in reference to that matter, only make one or two additional observations Dr. Kunth based his statements on a single specimen in a bad state of preservation. His figure shows how inadequate the specimen is to support his views. Out of the many hundreds—I may even say thousands—of specimens of Heterostraci which have passed through my hands, I could easily pick several exhibiting all varieties of juxtaposition of Pteraspis with Scaphaspis, and of specimens of a single species of either genus with other specimens of the same species. The packing of several shields one within another not unfrequently occurs, as happens very generally in the embedding of concave shells. The mere association of these shields, as in Gallicia and in Herefordshire, is not a phenomenon on which any one familiar with them—through examination of numbers of specimens from various localities—would venture to base any argument as to structural connexion.