364 Annals of the Carnegie Museum. 



Amp/lion Canadensis Billings, 1 859, Canadian Naturalist and Geologist, volume IV, 



page 381, figure 12 a, I). 

 Amp/iiflii Canadensis Billings, 1863, (leology of Canada, page 133, figure 69. 

 Atuphiou Canadensis Billings, 1865, Paleozoic Fossils Canada, volume i, page 288, 



figure 278. 



This abundant species, which is the only one of the Chazy trilobites 

 of which entire specimens are at all common, can now be figured and 

 described from very complete material. Most of the whole specimens 

 obtained by the writer have been taken from the rocks immediately 

 south of Tiger Point, on the east side of Valcour Island. In all cases, 

 they were found in pockets of mud which occur with some frequency 

 in an otherwise fairly pure limestone. Another locality, which has 

 furnished very satisfactory specimens, is the point at the southeast end 

 of Valcour Island, where the specimens also occur in muddy layers. 

 Nearly all the specimens are more or less distorted, the distortion 

 occurring at the points which are nearest the limestone and covered 

 by the thinnest coating of the clay. Although these specimens are 

 usually found stretched out in the natural position, an occasional 

 enrolled specimen is found in the same layers. While these localities 

 have furnished the most satisfactory specimens, the matrix in which 

 the species occurs most freely is the pure buff dolomite of the reefs. 

 Those layers about Smuggler's Bay contain vast numbers of whole 

 and fragmentary specimens, which are, however, of little use to the 

 collector as they cannot be extracted without removing a large part or 

 all of the test. 



Description. 



Cephalon wide, short, rather uniformly convex. Glabella gently 

 convex, broadly rounded in front. There are three pairs of glabellar 

 furrows, the first pair being very close to the anterior margin and not 

 very deeply impressed. They vary in direction on different speci- 

 mens, sometimes running somewhat forward, while, in other specimens, 

 they are curved backward. The second and third pairs run very 

 nearly perpendicular to the axis and about half way to the center of 

 the glabella. Fixed cheeks large, including the genal angles which 

 are rounded and without spines. Free cheeks small. Eyes prominent, 

 0])posite the second glabellar lobes and situated at a distance from the 

 glabella equal to about their own width. The entire cephalon is sur- 

 rounded by a wide, convex border which is outlined by a deep furrow. 

 Surface granular. 



