418 ME. F. R. COWPER REED ON THE [Allg. 1 896, 



the axis of the pygidium and extends to a prominent, triangular, 

 articulating process which euds the narrow articulating band on the 

 straight anterior edge of this portion. Beyond this articulating 

 process the pleura becomes free and bends back at an angle of 70° 

 to the anterior edge of the inner portion. This free or outer 

 portion of the pleura is produced into a long flattened spine, part of 

 which is broken off in our specimens. A strong oblique furrow 

 traverses the inner portion of this pleura and is accompanied by a 

 ridging-up of the surface on each side of it. Just before the pleura 

 becomes free it attains its greatest width, which is equal to half the 

 entire length of the pygidium itself. The outer or free portion 

 tapers gradually backward and diverges from the second pleura at 

 an angle of about 50°. The point at which this divergence com- 

 mences is situated at the level of the anterior edge of the single, 

 median, subterminal piece of the pygidium. 



The pleurae of the second segment are directed backward, and 

 their free portions consist of spines running back parallel to the 

 axis. The inner portion of each of these pleurae has an anterior 

 border slightly curved forwards and outwards, but the anterior, or 

 rather outer, edge of the free portion is almost straight. The 

 greatest width of this pleura is across the base of the free portion, 

 as in the first pleura, but it does not amount to more than two-thirds 

 of the greatest width of the first pleura. The spine of the second 

 pleura, in addition to being more rounded and slender, cannot have 

 been more than half as long as that of the first pleura. Neither 

 the inner nor outer portion of the second pleura hears any furrow 

 on its surface. 



Each pleura of the third pair has its proximal or anterior portion 

 only about one-third of the greatest width of the second pleura, 

 with which it is in contact for the whole length of its proximal 

 portion. These proximal portions of the third pair of pleurae are 

 directed backward and slightly inward, but nearly parallel to the 

 axis of the pygidium and to each other. The flattened distal 

 portions are not in contact with the second pleurae, but bend sharply 

 inward in close contact with the median posterior piece of the 

 pygidium, and become nearly double the width of the proximal 

 portions, to end each in a blunt point. 



The median terminal, or rather subterminal, piece of the pygidium 

 is triangular in shape and is completely embraced laterally and 

 posteriorly by the third pair of pleurae, so that the posterior end of 

 the pygidium has a bifurcate appearance owing to the bluntly- 

 pointed extremities of this pair of pleurae. There is no furrow on 

 the last pair of pleurae or on the median subterminal piece. 



The axis of the pygidium is triangular in shape, it tapers 

 rather rapidly posteriorly, and its sides meet at the apex of the 

 median subterminal piece at an angle of about 60°. The axis is very 

 slightly convex and not much raised above the pleural portions of 

 the pygidium. It is furnished with three rings, of which the first 

 is rather broader than the posterior two, which are of equal breadth. 

 Each ring is rounded and, owing to the extreme weakness and 



