New Species of Trilobites, 373 



upper sides, but on the inner side even with the surface ; the dis- 

 tance between its outer side and the dorsal furrow appears to be 

 a little variable, but is always more than half the width of the 

 axis of the thorax at the first segment, or about one-sixth the 

 whole width of the head ; it is distant from the posterior margin 

 rather less than its own diameter. The facial suture turns out- 

 wards and cuts the posterior margin at a point just behind the 

 outside of the eye; it cuts the front margin on a parallel passing 

 half-way between the eye and the dorsal furrow. 



Thorax with eight segments, the axis very convex and well 

 defined by nearly straight sides ; it gradually tapers so that the 

 width of the last segment is only about two-thirds that of the 

 first. The space on each side between the axis and the bend of 

 the pleurae is perfectly flat. The bend of the first pleura takes 

 place at one-third its length or half-way between the axis and the 

 parallel of the outer side of the eye, in the last pleura it is a 

 little more distant. 



The pygidium is snb-quadrilateral, the front margin straight 

 with the exception of the convex elevation of the axis in the 

 middle third ; the lateral extremities are largely truncated, 

 straight, aud at an angle of about 80° with the straight portion 

 of the anterior border ; the posterior margin is gently convex. 

 The axis is very prominent in front but becomes obsolete or 

 scarcely at all defined behind. The width of the pygidium is not 

 quite twice the length. 



The surface is strongly punctate. 



The fragments such as the heads and tails are not uncommon 

 but perfect specimens extremely rare. The following are the 

 measurements as nearly as they can be made out from a single 

 rolled up specimen which has the lateral extremities of the head 

 broken off, but is in other respects beautifully perfect. 



Length of head in straight line b\ lines. 



following curvature 7 " 



Distance between dorsal furrows 4 M 



Outside of eye from dorsal furrow 2\ u 



Distance of eye from posterior margin § " 



Diameter of eye front to rear ^ " 



Length of thorax 4£ " 



Width of axis at first segment 3 \ u 



at last segment 2 J u 



Bend of first pleura from axis l{ " 



last pleura 1 



$ " 



Length of Pygidium 4 



