48 BRITISH FOSSILS. 



provisionally as belonging to them. The filament c, I, consists of at 

 least four elongate sublinear joints, besides a basal one, or probably 

 two, which are short and obscure. The first of the long joints is 

 rather swelled and crenulate or spinose at the tip (at*) ; the next, 

 which is about four times as long as broad, shows some little 

 crenulation. 



Of the branched filament (or pair of filaments) h, i, the junction 

 with the maxilla is quite obscure ; there are about three linear joints 

 to each, broader than those of the palpus c, L The detached fragment 

 m, if it belong to this specimen at all, would from its size correspond 

 to one of this pair (h, for instance, rather than V). 



5. Swimming Feet, Plate I. figs. 13*, 14. Fig. 13* is found at- 

 tached to the carapace, above described, which has the maxillae and 

 palpi, &c. attached. Fig. 14 lies loose in the same slab, and as it is 

 materially different from that of the other large Lanarkshire species 

 (P. acuminatus, Plate II.), belongs, no doubt, to this. The basal 

 joint (fig. 14) is less expanded in the lower part than in H. bilobus. 

 It is rudely trigonal, the sides convex but not equal, the forward edge 

 (14 a) being shortest, and the lower angle d produced. The neck 

 is rather broad, and the terminal lobe linear-oblong, with a straight 

 serrate edge. The teeth are fourteen, besides the small lower lobe 

 b, short and conical, and very obliquely set. The surface is closely 

 plicate (fig. 14 a) nearly all over. 



The other joints, fig. 13*, are very obscure, but constitute a linear 

 swimming paddle, but little bent, like that of H. bilobus. The second 

 joint is lost, but the third (i) is linear, the fourth (m) triangular, 

 and the fifth (ca) irregular and obscure in the specimen. The 

 penultimate joint and terminal palette (p, d) are much distorted ; 

 but in a fine specimen of the carapace, with the swimming feet 

 (ectognaths) attached, and which was discovered by Mr. Slimon 

 since the plates were finished, the penultimate joint (p) is more 

 than twice as wide as long, with a strong process from its hinder 

 angle running upwards, and a deeply notched termination to 

 receive the terminal oval palette. This last is short and narrow, com- 

 pared with that of P. bilobus. (See woodcut, fig. 3.) The two ecto- 

 gnaths are very perfect ; they are attached at the outer angle, but 

 turned outwards in this specimen by decomposition of the attaching 

 muscles, so that the exterior margins are placed opposite to each 

 other, and the inner serrated lobes look outwards (the dotted lines 



