On exactly the same grounds I infer that certain large coprolites of common occurrence in the Thurso flagstones, which contain the broken scales of Dipterians, and exhibit a curiously twisted form, (fig. 44,) also belonged to the _Asterolepis_; and from these, that the creature was carnivorous in its habits,—an inference which the character of its teeth fully corroborates; and farther, that, like the sharks and rays, and some of the extinct Enaliosaurs, it possessed the spiral disposition of intestine. Paley, in his chapter on the compensatory contrivances palpable in the structure of various animals, refers to a peculiar substitutory provision which occurs in a certain amphibious animal described in the Memoirs of the French Academy. “The reader will remember,” he says, “what we have already observed concerning the _intestinal_ canal,—that its length, so many times exceeding that of the body, promotes the extraction of the chyle from the aliment, by giving room for the lacteal vessels to act upon it through a greater space. This long intestine, whenever it occurs, is in other animals disposed in the abdomen from side to side, in returning folds. But in the animal now under our notice, the matter is managed otherwise. The same intention is mechanically effectuated, but by a mechanism of a different kind. The animal of which I speak is an amphibious quadruped, which our authors call the Alopecias or sea-fox. The intestine is straight from one end to the other but in this straight, and consequently short intestine, is a winding, cork-screw, spiral passage, through which the food, not without several circumvolutions, and, in fact, by a long route, is conducted to its exit. Here the shortness of the gut is _compensated_ by the obliquity of the perforation.” This structure of intestine, which all the true Placoids possess, and at least the Sturiones among existing Ganoids, seems to have been an exceedingly common one during both the Palæozoic and Secondary periods. It has left its impress on all the better preserved coprolites of the Coal Measures, so abundant in the shales of Newhaven and Burdie House, and on those of the Lias and Chalk. It seems to be equally a characteristic of well nigh all the bulkier coprolites of the Lower Old Red Sandstone.[19] In these, however, it manifests a peculiar trait, which I have failed to detect in any of the recent fishes; nor have I yet seen it indicated, in at least the same degree, by the Carboniferous or Secondary coprolitic remains. In the bowels which moulded the coprolites of Lyme-Regis, of the Chalk, and of the Newhaven and Granton beds, a single screw must have winded within the cylindrical tube, as a turnpike stair winds within its hollow shaft; and such also is the arrangement in the existing Sharks and Rays; whereas the bowels which moulded the coprolites of the Lower Old Red Sandstone must have been traversed by triple or quadruple screws laid closely together, as we find