214 On the Geology of the Island of Montreal. 



are yet to be stated. All its varieties furnish the same animal 

 remains ; but no fossil vegetables have yet been found. They 

 are chiefly sparry or granular casts of the common limestone. 

 Lingulce, however, and terebratula, frequently preserve their 

 nacre. Of trilobites, the asaph genus is the most abundant, 

 excepting perhaps the debris of very large trilobites, usually 

 too comminuted to allow of the determination of the species ; 

 but in the crystalline limestone of the quarries, they are larger, 

 and are evidently caudal portions of the genus lsotelus, lately 

 instituted by Dr. Dekay. Some of them, although represent- 

 ing at least one third of the animal, are only a quarter of an 

 inch long. The asaphs approach nearest the species cau- 

 datus of Brongniart. I have found no entire Calymene : but 

 many bucklers or heads of the Blumenbach species ; and some 

 of them an inch and an half in diameter. They are found 

 whole, in considerable numbers, in the vicinity of Quebec. 



The fragments of trilobites, from Germany, and Llandillo in 

 Wales, represented in fig. No. 6. &tc. of Brongniart, occur 

 plentifully here, and do not differ much from those of the above 

 distinguished naturalist, in general outline and dimensions.* 

 The front of the buckler is much more convex, remarkably so ; 

 and has on each side, near the base, three very small trans- 

 verse lines, (scarcely to be called depressions) corresponding 

 to the sulci so strongly marked in the genus Calymene. There 

 is frequently, but not universally, a very minute pisiform pro- 

 cess on the centre of the front. The whole upper edge of the 

 buckler is always surrounded by a very ornamental semicir- 

 cular border (sometimes semi-elliptical) of punctures, placed 

 in the meshes of a net-work in high relief, and arranged close 

 together, in rays, passing perpendicularly from the buckler, 

 and forming at the same time, when observed transversely, 



* At Montmorenci, near Quebec, they occur much larger : rather ex- 

 ceeding: one and a half inch in diameter. 



