166 THE CANADIAN NATURALIST. [Vol. viii. 



if accumulated in mass, might form more or less continuous 

 beds. 



The food of the animals producing such coprolites can scarcely 

 have been vegetable ; for though marine plants collect and con- 

 tain phosphates, the quantity in these is very minute, and 

 usually not more than that required by the animals feeding on 

 them. 



We must therefore look to the animal kingdom for such 

 highly phosphatic food. Here we find that a large proportion 

 of the animals inhabiting the primordial seas employed calcic 

 phosphate in the construction of their hard parts. Dr. Hunt 

 has shown that the shells of Lingula and some of its allies are 

 composed of calcic phosphate : and he has found the same to be 

 the case with certain Pteropods, as Conularia, and with the sup- 

 posed worm-tubes called Serpulites, which, however, are very 

 different in structure from the tubes above referred to. 



It has long been known that the crusts of modern Crustaceans 

 contain a notable percentage of calcic phosphate ; and Hicks and 

 Hudleston have shown that this is the case also with the Cam- 

 brian Trilobites. Dr. Harrington has kindly verified this for 

 me by analyzing a specimen of highly trilobitic limestone from 

 the Lower Potsdam formation at St. Simon, in which the crusts 

 of these animals are so well preserved that they show their min- 

 utely tubulated structure in great perfection under the micros- 

 cope. He finds the percentage of calcic phosphate due to these 

 crusts to be 1-49 per cent, of the whole mass. It is to be ob- 

 served, however, that the crusts of Trilobites must have consisted 

 very largely of chitinous matter, which, in some cases, still exist 

 in them in a carbonized state. A crust of the modern Limulus, 

 or King Crab, which I had supposed might resemble in this 

 respect that of the Trilobites, was analyzed also by Dr. Harring- 

 ton. It belonged to a half grown individual, measuring 525 

 inches across, and was found to contain only 1845 per cent, of 

 ashes, and of this only 1*51 per cent, of calcic phosphate. The 

 crusts of some Trilobites may have contained as large a propor- 

 tion of organic matter ; but they would seem to have been richer 

 in phosphates. Next to Ling nice and Trilobites, the most abun- 

 dant fossils in the formations containing the phosphatic nodules 

 are the shells of the genus Ilyolithes, of which several species 

 have been described by Mr. Billings*. Dr. Harrington has 



* Canadian Naturalist, Dec. 1871. 



