BRITISH FOSSILS. 



8^ 



does not show whether these tubercles have each a pit on their 

 summit ; it is probable they are so constructed, like those of the 

 other species in the genus. The raised fascia, too, in front, has so 

 worn a surface that tubercles are not visible, if they ever existed. 

 The cheeks, instead of being tuberculate, are pitted like those of 

 Cheirurus or Amphion, and the raised interstices are covered with 

 fine granules. The margins appear smooth, or only finely granular. 

 We have no specimens of the hypostome, or indeed any part of 

 the under surface of the animal. 



The thorax consists of 11 segments; the axis moderately con- 

 vex, of nearly equal breadth throughout, and considerably nar- 

 rower than the pleurae. These are quite horizontal as far as the 

 fulcrum, which is placed more than half-way from the axis ; and from 

 this point they curve backward and downward to the tip, which 

 is again a little bent forward, so that the line from the fulcrum 

 outwa,rds is a sigmoid curve ; the hinder pleurae curve less backward. 

 Each pleura is nearly semicylindrical, with three or four tubercles 

 along it, and there is little or no space anteriorly for the narrow flat 

 rim which exists in the species of Cyhele, and which we have called 

 sometimes the fulcral portion.* We have not the extreme ends 

 preserved ; but from what has been observed in E. pundatus and 

 K variolaris, there is little doubt it was terminated by a bilobed 

 tip, such aB we have indicated by dots in fig. 7 ; the notch c being 

 in front of the blunt outer tip, and indenting the end of the facet h. 

 This facetted or flattened portion, which passes beneath the pre- 

 ceding ring in rolling, is shown in fig. 8, a. 



Tail of a triangular form, wider by one third than the length, 

 with an obtuse rounded apex, and flattened above, the sides and the 

 tip deflected, so that the tail is moderately convex ; the axis at the 

 upper part is about one fourth the width of the tail, and tapers to a 

 point at some little distance within the blunt apex ; it is convex at 

 its broadest end, and there the rings are continuous across, but from 

 about the upper third it becomes flatter, and the rings are effaced 

 along the middle ; its apex is quite flat. There are about 20 

 rings in all, and no tubercles down the smooth central portion. 

 The sides of the tail have six strong ribs, which are broad and 

 somewhat flattened, divided from each other by narrow deep 

 furrows, and have the tips squarish and obtuse. The ends of the 



* Tn this genus, as in Amphion, Acidaspis, and some others, the pleura is not divided by 

 a groove along its middle as it is in Cahjmene ; the division into two parts, an anterior or 

 fulcral portion and a posterior portion, exists, hut the latter occupies nearly all the outer 

 surface of the pleura. 



