602 Annals ok thk CAR\F.f;iE Muskum. 



prominent, convex, and about one third the width of the thorax. 

 The pleura are flat on the dorsal surface and rather sharply deflected 

 at the sides, where perfect. As shown by 'he figure, the ends of 

 nearly all the thoracic segments are broken on one side, and of the 

 first five on both sides, so that their terminations cannot be made 

 out. On each side of the axial lobe, each segment bears three pustules, 

 the one nearest the median line being most prominent, while the two 

 which are lower are very faint. The distal portion of each segment 

 bears two or three rather prominent pustules, as do also the ribs on 

 the pleura of the pygidium. On the pleura of the thorax each seg- 

 ment bears a deep groove which divides it into two convex portions. 

 The anterior one is slightly smaller than the posterior in the first six 

 segments, and back of that the two portions become even more differ- 

 entiated. The posterior portion becomes swollen and somewhat club- 

 or paddle-shaped, while the anterior portion becomes small and slips 

 under the i)Osterior portion of the segment ahead. Where the anterior 

 portion of one segment strikes the posterior portion of the segment 

 ahead, there is a narrow flange on the forward segment. This flange 

 becomes more strongly developed and nearer the axis as the ]n'gidium 

 is approached, and is especially well formed on the l)ack of the 

 twelfth segment. The thorax is 7 millimeters long, 12 millimeters 

 wide at the anterior end, and 5 millimeters wide at the posterior end. 

 The axial lobe is 4.5 millimeters wide at the back of the cephalon, 

 and 1.5 millimeters wide on the twelfth segment. 



The pygidium is very small, about as wide as long. The axial lobe 

 is wide and i)rominent, the pleura narrow and depressed. On the 

 pleura are four pairs of double ribs, the first pair of which are larger 

 than the others, and form a sort of anterior and lateral border to the 

 pygidium. The axial lobe bears five pairs of small jiustules, and has 

 fifteen or sixteen transverse furrows which show only on the sides, and 

 do not cross the flattened top. These transverse furrows occur over 

 nearly the whole length of the axial lobe, which does not reach the 

 posterior border of the pygidium. At the posterior end of the median 

 lobe is a rather prominent, unpaired tubercle. The ribs of the pleura 

 bear small tubercles in pairs, and end in short, blunt spines. 



Locality. — The specimen here described and figured was found by 

 Mr. J. E. Narraway in the Black River limestone on the Ontario side 

 of the Petite Chaudiere, near Ottawa, Canada, and is in his private 

 collection. 



