regard the creature as an extinct crustaceous animal, and some as belonging to a tribe closely allied to the _Chelonia_. Agassiz, as the writer of these chapters ventured some months ago to predict, has since pronounced it a fish--a _Pterichthys_ specifically different from the five varieties of this ichthyolite which occur in the lower formation of the system, but generically the same. I very lately enjoyed the pleasure of examining the _bona fide_ ichthyolite itself--one of the specimens of Dura Den, and apparently one of the more entire--in the collection of Professor Fleming. Its character as a _Pterichthys_ I found very obvious; but neither the Professor nor myself was ingenious enough to discover in it any trace of the beetle of Dr. Anderson.[AT] [Footnote AT: This interesting ichthyolite has since been regarded by Agassiz as the representative of a distinct genus, to which he gives the name _Pamphractus_. As exhibited in his restoration, however, it seems to differ little, if at all, (if I may venture the suggestion,) from a Pterichthys viewed on the upper side. In Agassiz's beautiful restoration of Pterichthys, and his accompanying prints of the fossils illustrative of that genus, it is, with but one doubtful exception, the under side of the animal that is presented; and hence a striking difference apparent between his representations of the two genera, which would scarce obtain had the upper, not the under side of _Pterichthys_ been exhibited. In verification of this remark, let the reader who has access to the _Monographic Poissons Fossiles_ compare the restoration of _Pamphractus_ (Old Red, Tab. VI., fig. 2) with the upper side of _Pterichthys_, as figured in this volume, Plate I., fig. 1, making, of course, the due allowance for a difference of species.]