DESCRIPTION OF THE SPECIES OF PTERYGOTUS 213 
provisionally as belonging to them. The filament ¢, /, 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) /, 2, the junction 
with the maxilla is quite obscure ; there are about three linear joints 
to each, broader than those of the palpus, c,/. The detached fragment 
m, if it belong to this specimen at all, would from its size correspond 
to one of this pair (/, for instance, rather than Z). 
5. Swimming Feet, Plate I. [Plate 12] figs. 13*, 14.—Fig. 13* is 
found attached to the carapace, above described, which has the 
maxilla 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. [Plate 13] ), belongs, 
no doubt, to this. The basal joint (fig. 14) is less expanded in the 
lower part than in H. dzfobus. It is rudely trigonal, the sides convex 
but not equal, the forward edge (14 a) being shortest, and the lower 
angle @ 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 4, short and conical, and very 
obliquely set. The surface is closely plicate (fig. 14 @) nearly all 
over. 
The other joints, fig. 13*, are very obscure, but constitute a linear 
swimming paddle, but little bent, like that of . dzlobus. The second 
joint is lost, but the third (7) is linear, the fourth (vz) triangular, 
and the fifth (ca) irregular and obscure in the specimen. The 
penultimate joint and terminal palette (f, 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 (f) 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, compared 
with that of P. dzlobus. (See woodcut, fig. 3.) The two ectognaths 
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 show what 
was their original position). The shape of the carapace is distinctly 
shown in this specimen. 
