BRITISH FOSSILS. 85 



from a portion of the body further back than fig. 3, for the squamjB 

 cover the whole lower surface of the segment (fig. 5), and the greater 

 part of the upper side (fig. 4). They are greatly more convex than 

 in the Scotch species, the posterior ones especially being parabolic 

 or even pointed in form, frequently three-tenths of an inch long and 

 broad. Fig. 5 shows the closely squamate lateral edges of the 

 segment, which are convex and rounded in the forward portion and 

 sharply keeled behind. The front margin in both of these segments 

 is contracted, for articulation with the previous joint, and has a 

 broad groove running along its whole length. The hinder angles 

 are a little produced. 



Penultimate segment, figs. 6, 7, 8, 9, and Plate IX. fig. 15. This 

 joint is much wider than long, in the proportion of four inches and a 

 half to two inches and a half ; some specimens must have been fully 

 five inches long, and therefore nine or ten broad. The segment is 

 widest and flattest at the hinder end, the margins are compressed 

 and keeled, except at the thickened and contracted base, and the 

 angles (fig. 9) pointed and produced. The upper surface (fig. 7) is 

 gently convex, but without any ridge, while the lower (?) fig. 6 has 

 a short thick keel extending half way up. It terminates on the 

 hinder margin of the segment, which is rather deeply notched at this 

 point. The surface is thickly covered with plicae, both above and 

 below, ' but they are much more prominent on the lower (keeled) 

 surface than on the other, where they are mere surface markings 

 and often obliterated. They cover the whole of the segment, but 

 are less thickly placed towards the hinder margin, at least on the 

 under side (fig. 6). The margin itself is tubercular. 



The squamate keeled lateral borders are ornamented with several 

 (about four or five) rows of oblique thick plicae, more prominent and 

 larger on the lower side ; these are continued from about the ante- 

 rior fourth of the segment, where the keel commences, to the pointed 

 hinder angle. Similar, but still larger, plicaB cover the central keel, 

 Plate IX. fig. 15a, and numerous shallow folds run obliquely back- 

 wards from the sides to the keel. 



Telson or Tail- Joint, Plate IX. figs. 16, 17. The dimensions of 

 this joint give the best indication of the size to which the species 

 grew ; its length was full five inches and the width four and a 

 half. The largest specimens of this part in P. anglicus, Plate V. 

 fig. 5, are rather longer but narrower. The general shape was that 

 of a broad and pretty regular oval, but truncated at the base, and 

 emarginate at the apex.* The underside, fig. 156, is flat, except 



* Plate IX. fig. 15, is the only specimen which shows the apex. Perhaps there nay 

 have been a short central apiculus, as in P. anylicus. 



