PTERYGOTUS ANGLICUS. 37 
presents a finely punctated appearance, as represented in Plate I, fig. 2a, but there is no 
appearance of any scale-like markings upon it, as upon the appendages and somites. 
The chelate Antenné.—The very fine examples of these organs drawn on Plate VII, 
figs. 1—3, from specimens in the museum of Lady Kinnaird, Rossie Priory, Perthshire, 
and the Watt Institution, Dundee, still remain unrivalled. Three joints at least may be 
observed in this member. ‘“ ‘The first is an elongated subcylindrical stem, flattened by 
pressure,” in fig. 2, but retaining its normal rounded form in fig. 4; ‘‘the next, short, 
enlarged, and swollen, is produced into a long slender process, pointed and incurved at 
its extremity, and beset with very strong and numerous unequal striated teeth. The third 
joint is articulated with the enlarged basal joint of the second, so that its similarly in- 
curved extremity is opposable, like a thumb, to the latter. It possesses teeth of a similar 
structure to those in the other ramus of the chela, and opposed to them as the canine 
teeth in the upper jaw of a mammal are opposed to those in the lower, passing, that is, 
behind the others, or on their proximal side.”” 
From a careful comparison of these organs with the less rare and often better preserved 
remains of Pferygotus bilobus and P. perornatus, they have been placed in front of the 
mouth (Plate VIII, figs. 1, and 2, 2,2). We have no evidence that the coxal, or basal joints 
of these chelate appendages were converted into gnathites ; but the corresponding simple 
pair of organs in Slimonia and Eurypterus (and probably also in Sty/onurus), arg made to 
fulfil the office of jaws. It was probably this fact, which led Prof. Agassiz? to conclude 
that the antennary system was entirely absent in the Hurypterida, but the antenne in 
Limulus (sce Plate IX, fig. 1, 3, and 1a) also act as gnathites; and if we accept Prof. 
Huxley’s view, that these chelate organs in Pferygotus represent the antennz, and assume 
the antennules to be aborted, the remaining mouth-organs will be found to correspond 
exactly in number, with Limulus. 
The Endognaths, or Mandibles and Mazille..—The three pairs of organs which follow 
after the antenne are apparently almost identical in form. 
At Plate VII, figs. 5, 6, 7 and 8, represent the best detached examples of these 
appendages that have as yet been discovered, whilst at Plate II, fig. 1, we see several 
nearly entire endognaths, but too small to show more than the general outline. 
The basal joint is large and flat, and produced almost to a point at one extremity 
(figs. 5p and 6p), where it was evidently attached to the head, and truncated obliquely to 
its long axis at the other. The truncated margin is slightly curved, and is beset with 
strong curved and pointed teeth, which are longer at one end of the series (a), than at the 
other (4), and are so constricted at their bases as to appear to be articulated with the basal 
joint (a, 4, figs. 5,6 and 7). On the outer part, immediately above the pointed extremity 
(p), is inserted the basal joint of the long palpiform appendage. ‘The first two (?) joints of 
1 Prof. T. H. Huxley, Surv. Mon., p. 14. 
2 Hall’s ‘ Paleontology of New York,’ 1859 (see ante, p. 18, 4 47). 
3 This description is taken im part from Prof. Huxley’s Survey Mon., p. 15 (4). 
