BRITISH FOSSILS. 91 



probably the tenth or last but two of the segments. Both show 

 the minute interspersed plica3 very clearly, and these small plicae 

 extend over nearly all the segment, while the larger ones are 

 confined to the anterior half. 



Telson, as yet unknown, as also is the epistomian plate. 



Antenna, Plate XII. figs. 7-1 0. Fig. 10 is most probably part of 

 the stem, and shows the large and small plicae in perfection. Figs. 

 7 to 9, the large characteristic chelaB, which can scarcely be con- 

 founded with any other species, the teeth being so much elongated. 

 Fig. 7 is the fixed claw, with a widely expanded and largely dentate 

 base.* The shaft is parallel-sided (not tapering as in P. ludensis), 

 and the teeth long-lanceolate, the large one being much longer than 

 the diameter of the shaft, (in fig. 7, fully three-quarters of an inch 

 long,) the secondaries three or four on each side of it, with small 

 teeth interspersed, all linear-lanceolate, erect and remote, not 

 crowded at their bases. In the fixed ranms they are either erect 

 or (fig. 8) point forward a very little. 



The striae on the teeth are very fine and close, f oblique some- 

 what on the great tooth, and more direct in the smaller ones. In 

 P. gigas and P. ludensis they are coarser, and the teeth broad. 

 The great terminal mucro is as broad and long as the primary 

 tooth, or even longer, and is bent at right angles to the shaft. 



Swimming Feet, Basal Joint, Plate XII. figs. 11-14. Several 

 fragments have been found of the great basal joint, and one 

 tolerably perfect from the Whitcliffe, Ludlow, fig. 11. It shows a 

 wide-expanded basal lobe, and the whole extent of the serrate tip, 

 with the usual number of teeth (thirteen, or rather twelve in this 

 specimen) ; and in fig. 14, the upper tooth being obsolete. Fig. 13 a, 

 from Ludlow, shows the full number. 



The lobe in front of the teeth is arched and thickened in all the 

 specimens, (a character in which this species differs widely from 

 P. anglicus,} and the second tooth is more than twice the breadth 

 of any of the others, conical, and but little curved ; the remaining 

 teeth are long, straight, narrow, and separated by about their width 

 from each other in large specimens. These elongate teeth are very 



* See P. ludensis (Plate XIV. fig. 10) for a similar chela. 



f See also Strickland's figure, quoted above. There is one lanceolate fragment (2 i) 

 in that figure, here reproduced, fig. 9*, -which is striated finely like the teeth. It 

 is serrated all down one side. Its nature is quite doubtful ; but it is associated with the 

 antenna ; and as the large primary tooth in P. gigas (Plate IX. fig. 3) is serrated posteriorly, 

 it is possible this may be the case in one of the chelae of the present species. There is 

 a small conical uncinate appendage in the same figure, Geol. Journ., that is yet un- 

 explained. Quart. Journ. Geol. Soc., 1. c. 



