380 New Species of Trilobites. 



one line from the dorsal furrow, or one-third the length of the 

 side-lobe. Outside of the fulcral angle the corner of the pygid- 

 ium is strongly folded down or bevelled as it were to permit of 

 the pleurse sliding over it in the act of rolling up. The dorsal 

 furrow is broad and shallow and its direction is remarkable; at 

 about half a line from the anterior margin it curves outwards, so 

 that in a distance of five lines the middle of the furrow has ap- 

 proached to within one line of the lateral margin, at which dis- 

 tance it continues all round ; the furrow is wide, shallow, broadly 

 concave, and not so distinct at the posterior margin as it is in the 

 anterior half. In consequence of this peculiar course of the dor- 

 sal furrow, the axis or central lobe instead of being conical and 

 small as it is in other species is sub-orbicular and occupies nearly 

 the whole superficies of the pygidium. In this respect this spe- 

 cies differs widely from any of those above described. The 

 pygidium is rather strongly and evenly convex, and the surface 

 is smooth. The width of the middle lobe of the anterior margin 

 appears to shew that the axis of the thorax is nearly equal to 

 two-thirds the whole width. 



Locality and formation. — Gem ache Bay, Anticosti, base of the 

 Middle Silurian. 



Ill^enus grandis. (n.s.) 



Description. — Very large, the fragments indicating individuals 

 eight or nine inches in length. The pygidium transversely sub- 

 oval, strongly trilobed in front, the anterior lateral angles largely 

 truncated, and the outline of the posterior two-thirds very nearly 

 a semicircle or rather a depressed cone. The central lobe of the 

 front margin of the pygidium is convex and nearly half the whole 

 width, being in the proportion of 11 to 26. The margin on each 

 side of the central lobe is straight, and nearly at a right angle 

 with the longitudinal axis until it approaches the fulcrum when 

 it makes a short curve and turns back so as to make the fulcral 

 angle about 45.° The distance of the fulcral angle from the 

 dorsal furrow is about half the width of the middle lobe; 

 the length of the side caused by the truncation of the anterior 

 angles rather more than half. The anterior third of the pygidi- 

 um is flattened or depressed convex, but the margin all round is 

 suddenly curved down. The surface is smooth. 



A pygidium 25 lines wide is 18 lines in length. Only a frag- 

 ment of the thorax of this specimen is preserved, consisting of 



