1824.] Scientific Notices — Mineralogy. 313 



dirty greenish colour; and minute crystals of magnetic oxide of 

 iron are also found in it." 



" Petalite. — This rare mineral, not hitherto found on this 

 continent, occurs on the north shore of Lake Ontario, on the 

 beach in front of York, the capital of Upper Canada. It is a 

 rolled mass weighing about a ton, and has much glassy tremo- 

 lite interspersed, and two large veins of irregular shape, of an 

 aggregate of actynolite and calcareous spar. Close to this 

 bowlder lies a still larger of the ophicalcic family (a term used 

 by the French geologists to designate a rock composed of mar- 

 ble and serpentine) from Grenville, or Gananoque, and strewn 

 around are loose greenstones, sienites, and some Labrador feld- 

 spar." 



The secondary limestone of the St. Lawrence and its lakes, is 

 particularly rich in the number, novelty, and beauty of its organic 

 remains. In addition to many which are unknown elsewhere, it 

 abounds throughout its vast extent in those fossils which are 

 supposed to characterise the carboniferous limestone. A great 

 many of these substances have been described in the second part 

 of the sixth volume of the Transactions of the Geological 

 Society. No impressions of fish, nor of vegetables, have hitherto, 

 according to Dr. Bigsby (from whose paper this part of our 

 extract is taken), been discovered in the Canadas. 



The fossils enumerated by Dr. Bigsby are, Trilobite, an 

 exceedingly numerous, and almost universal family, always 

 found in fragments, but not unfrequently containing the greater 

 part of the fossil, with the remainder lying close by. 



" I have by me at present a fine but imperfect impression 

 from the cast of an undescribed trilobite from the isles un the 

 north shore of Lake Huron. It is a pretty exact oval, rather 

 exceeding five inches in length, and two and a half in breadth. 

 The total length appears to have been six inches. It is not 

 clear which end represents the ' bouclier ; ' except we judge 

 from the position of the articulations, which are eleven in num- 

 ber, each one-fifth of an inch broad, the upper one being an 

 inch and a half from the summit of the supposed bouclier. Of 

 the three lobes, the middle one is much the largest, that on each 

 side being only five-eighths of an inch broad, and being not 

 quite so protuberant as the first mentioned lobe, which itself has 

 a moderate and gradual convexity. All parts of this remain are 

 full of small transverse curved tracings, more or less parallel to 

 each other." 



Ammonite. — Casts of ammonites are found on the shores of 

 the Lakes Huron, Simcoe, and Ontario. 



Orthoceratites. — Found everywhere in immense quantities. In 

 Lake Huron they sometimes occur five feet long, but in the 

 Lake of the Woods and Lake Simcoe, little more than an inch 

 in length. " Major Delafield's collection contains a flattened 



