96 THE ASTEROLEPIS, 



very considerable size, — and that they formed no part of the 

 known fishes of the formation. 



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. 50), also belonged to the Astero- 

 lepis ; and from these, that the creature was carnivorous in 

 its habits, — an inference which the character of its teeth fully 

 coiToborates ; and farther, that, like the sharks and rays, and 

 some of the extinct Enaliosaurs, it possessed the spiral dispo- 

 sition of intestine. Paley, in his chapter on the compensa- 

 tory 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 me- 

 chanically 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 intes- 

 tine 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 intes- 

 tine, which all the true placoids possess, and at least the 

 Sturiones among existing ganoids, seems to have been an ex- 



