BEITISH FOSSILS. "73 



to this point might mislead in comparing with other species 

 (P. gigas, for instance, Plate VIII.), it is of consequence to note 

 this difference in the ornamentation of different portions. 



Appendages. 



Antennae, Plate VI. figs. 4, 6. They were of great size. Plate VI. 

 fig. 5, shows the largest we have seen, but a somewhat smaller size 

 (fig. 4) is not at all unfrequent. There are four joints, including the 

 free terminal claws. 



Of the first articulation only short fragments remain, it is nar- 

 rower than the second, which is linear, scarcely contracted at either 

 end, and in the largest specimen must have been four inches and 

 a half long and one inch and a quarter broad. The penultimate 

 joint, which is produced into the fixed claw of the chela, is rather 

 suddenly swelled, and increases in width outwards to the insertion 

 of the terminal joint. The produced portion is fully four inches 

 long, rather narrowed at its insertion (so as to be a little fusiform), 

 and thence tapering to the abruptly curved tip, which bends up at 

 a right angle, and is frequently half an inch long and pointed. The 

 opposed free claw is of the same shape, but more equal in breadth, 

 generally longer, fig. 2, than the other, but sometimes the two are 

 nearly equal (fig. 1). Occasionally the moveable joint is largest, 

 fig. 6, and overhangs the other considerably. 



It is difficult to say which was anterior, but from the curvature 

 probably the free joint was forward, as in our figure. Each half of 

 the forceps similarly armed with about four primary and ten or 

 eleven secondary teeth, three or four between each pair of primaries. 

 These are set on at right angles, or rather pointing a little forward 

 on the fixed finger, but on the moveable claw decidedly backwards. 

 They appear to have been much compressed, and were so long that 

 when the chela was closed they shut side by side like the blades of 

 a pair of shears ; and they are placed opposite to one another as if 

 for the purpose of cutting as well as seizing. The middle pairs are 

 longest, sometimes measuring half an inch. The pair next outwards 

 from these are nearest in size, and the outermost and innermost 

 pair (when the latter are present) are smallest. 



The shape of the large teeth and of many of the smaller is ovato- 

 lanceolate, constructed just above the immediate base, and then 

 expanded into a lancet form, and longitudinally striated, the strise 

 radiating a little from the base on the forward edge. Some of the 

 smaller teeth are simply conical, and the stria tion of all is about 

 equally coarse. 



