DESCRIPTION OF THE SPECIES OF PTERYGOTUS 261 
side towards the tip of the process. Here and there some striz are 
stronger than the rest. 
Near the base of the processes the striz are still more interrupted 
and run into short impressed lines or puncta. 
Plate XIII. [Plate 24] figs. 5, 6, 7, 11, and 18—These are from 
the UpPER LUDLOW Rock. Fig. 11 is a very perfect joint of the 
palpus, with both spines attached; and figs. 5 and 6 show the 
characteristic long plice; fig. 7, part of a chela probably of this 
species. Fig. 6 at least would answer best to one of the long joints 
of the antennz ; it is but a cylindrical fragment of the proximal end, 
and has the contraction which is visible in the corresponding joint of 
P. anglicus, Plate 1V. [Plate 15] fig. 4¢ At this part the plice 
are very numerous and small; in the body of the joint they are 
large, prominent, and elongate, and with the channel-like depres- 
sion and its bounding ridges, fig. 62, magnified. They are somewhat 
unequal in size, and set at more than their diameter apart from one 
another. 
Plate XIII. [Plate 24] ng. 18—There is one other fragment in 
the Upper Ludlow to which a place cannot be yet assigned, and yet 
belongs apparently to P. punctatus. It is a long strap-shaped piece, 
two inches and a half long and half an inch broad, and narrowed 
and rounded at one if not both ends. At @ it is imperfect. The 
surface shows the peculiar long tubercular plice of the species, at 
least near the base (2) and the opposite end 4, and the margins are 
deeply incised by short slits forming nearly square serrations (like 
those on the edge of the carapace of a crab). This is not exactly 
the structure of any part of the margin of Pverygotus, the usual 
ornament being that of prominent superficial plice or tubercles. 
The terminal (?) portion 4 differs in not having (so far as the impres- 
sion shows) this serrate edge, but only a thickened crenate margin 
and is probably a distinct joint, or may even be accidentally placed 
where it is. The surface shows elongate plicae of various sizes, rather 
thickly scattered. 
The Metastoma (Plate XI. [Plate 22] fig. 4) is nearly three 
times as wide as long, widest above the middle, and tapering back- 
wards with straight sides from this point to the blunt posterior 
extremity ; the anterior end is broadest, rounded, and not even emar- 
ginate; much less bilobed as in other species. It is thus quite 
different in shape from that of any other species ; its long oval form, 
blunt ends, and straightened sides enable us to recognise it at once. 
It occurs three inches and a half long; and in specimens of this size, 
the width is one inch and a quarter. 
