326 DESCRIPTION OF THE SPECIES OF PTERYGOTUS 
a ridge runs along the convexity, and another near the straight 
inner edge. The terminal serrate portion is narrow-oblong, and set 
very obliquely on the rhomboidal neck, from which it is obscurely 
divided. Its upper (forward) margin is strongly arched, and the 
straight serrate edge furnished with fourteen teeth, besides a promi- 
nence on the very small basal lobe. The uppermost tooth is minute, 
the second largest of all, but not greatly larger than the rest; all are 
short-conical, tolerably equal in size, and a little curved as well as set 
obliquely, pointing backwards. 
The remaining joints, figs. 7, 8, 9, are well exhibited in three or 
four specimens, of which fig. 7 shows the impression of the upper side 
(see for comparison Plate VI. [Plate 17] fig. 1). Figs. 8, 9, are 
impressions of the lower surface (see fig. 2 of the same plate). 
Basignathite—The second Joint @ is very narrow, almost linear, 
and fully three times as wide as long; the third (or zschyguathite) is 
linear (?) on the under surface (fig. 8 2) but greatly produced forwards 
on the upper (fig. 7), so as to touch, by its projecting boss, the fifth 
joint. The general form is rudely trigonal, or rather trapezoidal, the 
upper straight edge being only about half the breadth of the lower, 
which is sigmoid, and near the boss tumid. 
The fourth joint (erognathite) is spherical-triangular before and 
behind, but on the lower side (fig. 8) it is produced into a long 
straight process which fits the inner angle of the bend of the limb; 
a deep notch on the forward edge receives the condyle of the fifth 
joint. The outer or front margin is very convex, almost gibbous, 
and forms the prominent forward angle of the foot, which is more 
strongly bent than in any other species. 
The fifth joint (carpognathite) is narrow-linear on the upper side, 
but much broader beneath, about seven lines long by ten or eleven 
broad, with a rounded boss anteriorly about midway along the joint, 
and a deep sinus at the hinder edge to admit the great process from 
the— 
Sixth joint (proguathite). This is broad-linear, or oblong (the 
sides straight and parallel), not quite twice as long as broad, ex- 
clusive of the lobes above and below. The upper lobe is rounded, 
fitting into the posterior concavity on the margin of the preceding 
joint, the lower lobes are unequal, the hindermost being largest and 
most pointed, the forward one rounded and shorter, the notch deep, 
rather wide and straight edged at the point of attachment of the 
last joint (¢). 
(@.) Dactylognathite.) This is two and a half times as wide as 
long, contracted at the base, widest above its middle part, and end- 
