51 



Dr. John Bigsby, in his " List of Organic Re- 

 mains, occurring in the Canadas," states that the 

 A. caudatus is frequently met with, thrown up by the 

 water on the north shore of Lake Superior on the 

 bank of Rainy riverat the Lake of the Woods, and 

 at several other places. In some localities they are 

 astonishingly numerous, and so small as to be almost 

 microscopic. They occupy indiscriminately lime- 

 stone of every colour, but are most numerous in that 

 which is brown or crystallized. They are composed 

 of the kind of limestone in which they happen to be 

 embedded. 



We have seen a number of specimens of this species 

 in the Albany Institute, in Mr. Wetherill's cabinet, 

 and in the Baltimore Athenseum; but in all of them, 

 the abdomen and caudal extremity only remain per- 

 fect: from their exact resemblance, however, to the 

 same parts of the A. caudatus, figured by Brongniart, 

 (plate 2, fig. 4, D.) we have no hesitation with regard 

 to their identity. The description which we have 

 given of the buckler^ supposed to belong to our Asaph, 

 is therefore taken from Brongniart, whose specimens 

 were found at Dudley, the celebrated locality of the 

 C. Blumenbachii.* The coriaceous membrane, which 

 extends beyond the lateral lobes and forms the caudal 



* In the first volume, 2d series, of the Transactions of the 

 Geological Society of London, Mr. Weaver has published some 

 highly interesting observations on the fossils found in Glouces- 

 tershire, England. The A. caudatus, he states, is there found 

 in the transition limestone, though very much mutilated. (Vide 

 p. 326.) 



