370 New Species of Trilobiles. 



length, rather evenly convex, most prominent in the centre,, the 

 front margin broadly rounded, the posterior margin trilobed by 

 the dorsal furrows which are extended forward to about the middle 

 of the head but are only distinct for one fourth that distance ; 

 they at first incline towards each other and then becoming very 

 obscure curve outwards; on each side of the central lobe the pos- 

 terior margin is nearly straight as far as the eye when it gradually 

 curves forward and outward for one half the length of the head 

 when turning a broad rounded angle it merges into the front mar- 

 gin. In consequence of this peculiar form of the posterior margin 

 the genal angle in this species is in the front half of the lateral 

 margin of the head. The eye is of moderate size lunate and 

 within one fourth of its length from the margin. The facial suture 

 curves forward so as to cut the front margin considerably within 

 a longitudinal line drawn through the eye; behind the eye its 

 course is remarkable as it turns outwards and runs parallel with 

 the margin which it reaches at about three fourths the length of 

 the pleurae. The lower angle of the eye is distant from the dor- 

 sal idrrow a little less than half the width of the central lobe of 

 the posterior margin. The width of the cheek piece on a line 

 drawn transversely across the head at one third the distance from 

 the eye to the front is nearly equal to half the distance between 

 the eyes. In a vertical view of the head neither the full width of 

 the cheek piece nor the position of the genal angle can be seen 

 as the outline is fore-shortened, consequently in the figure above 

 given the width appears less than it really is. 



Thorax of ten articulations, axis of thorax square, the length 

 and breadth being the same, moderately convex, well defined ; the 

 fulcra of the pleurae are at about one third the width of the axis 

 from the dorsal furrow, the intervening space flat. 



Anterior edge of pygidium convex at the axal lobe, obliquely 

 truncated from the fulcrum, the axis either not at all or only very 

 obscurely defined. 



Surface smooth with the exception of the front of the head 

 where there are at the margin the usual transverse fissures. 



This species was discovered by Admiral Bayfield, R. N., during 

 his survey of the Gulf of the St. Lawrence. A well preserved spe- 

 cimen is in the Cabinet of the Geological Society of London 

 among the fossils presented by Admiral Bayfield. During the 

 present year 1859, Sir W. E. Logan visited the Mingan Islands 

 and procured numerous specimens at Trilobite Bay the original 

 locality. 



