DESCRIPTION OF THE SPECIES OF PTERYGOTUS 224 
chele 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 arguments 
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. [Plate 14] figs. 2, 5), and of 
size suitable to that of P. acumdnatus, occurs with it at Lesmahago. 
It is specifically different in the great length of the central lobe (2) 
which projects forward a long way beyond the side lobes or wings ; 
FIG. 5. 
Epistome of P. acuminatus ; half the natural size. 
or we may consider these latter as contracted (a). The whole piece 
is transverse, instead of rudely triangular, and the sculpture confined 
to the anterior border. The median lobe (4) is pyramidal, not 
sagittate, at the base; its tip is broken off. 
The occurrence of this more perfect specimen renders it unneces- 
sary to suppose that Plate XV. [Plate 26] fig. 3, should represent 
the central lobe of this organ. Nevertheless, it has the expanded 
sagittate base usual in this section of the genus, and from this base 
extends a narrow lanceolate piece, ridged along the centre, and 
shelving (to pass under the lateral lobes) on the sides. These contract 
