BRITISH FOSSILS. 59 



Appendages. 



Antennce, Plate II. figs. 2, 3. The position of these serrated 

 organs is settled by their mode of occurrence in the species previously 

 described. The fragments, figs. 2, 3, being the largest chelae in the 

 stratum, and, occurring also with this large species, probably belong 

 to it. The teeth are narrow, lanceolate, shorter than the width of 

 the shaft, turned a little backward, and closely striate. The three 

 primaries are rather more than their own length apart, and the 

 last rather more remote from the terminal tooth, which is curved 

 upwards nearly at a right angle. The secondary teeth are sharp- 

 conical, and five or six in each interspace. The shaft is rather 

 broad, its outer edge quite straight, and at the tip, which is blunt 

 and abrupt, strongly punctured for a short distance. The free 

 claw, fig. 2, has the usual contraction at its base. 



Oral Appendages. From a number of fine specimens from 

 Lesmahago, found since the plates were engraved, some excellent 

 additions have been made to this species ; these will be given in 

 woodcuts. They render, I think, unnecessary some of the argu- 

 ments used further on to prove the existence of two pairs of jaws 

 with their palpi, but as those refer to the evidence as it stands in 

 the plates, it is thought better to retain them. 



Epistoma, and labrum. A piece answering to the shape of this 

 organ in another species (see Plate III. figs. 2, 5), and of size 

 suitable to that of P. acuminatus, occurs with it at Lesmahago. 

 It is specifically different in the great length of the central lobe (6), 

 which projects forward a long way beyond the side lobes or wings ; 

 or we may consider these latter as contracted (a). The whole piece 

 is transverse, instead of rudely triangular, and the sculpture con- 

 fined to the anterior border. The median lobe (6) is pyramidal, 

 not sagittate, at the base ; its tip is broken off. 



Half the natural 

 size. 



The occurrence of this more perfect specimen renders it un- 

 necessary to suppose that Plate XV. fig. 3, should represent the 



