524 B. N. PEACH ON FURTHER RESEARCHES AMONG THE 
plates of the thoraco-abdomen the mummified remains of muscle, which can be 
teased out so as to exhibit its characters under the microscope. The fibres all lie 
parallel to each other, and at right angles to the breadth of the plates, that is, 
in the direction of the length of the body, as they do in the corresponding parts 
of the recent scorpions. 
It is necessary I should say something in defence of my position, in making 
a genus for the reception of these Eurypterids. The affinities of scorpion with 
Stylonurus and Pterygotus have often been pointed out, but in all these the 
cephalic appendages of which have been observed were undoubtedly aquatic. The 
appendages of the Carboniferous Eurypterus, however, have never before been 
studied to my knowledge, as that animal has been only known by the carapace 
and a few of the body segments. From these and the markings it has been 
inferred that their limbs were like those of the Old Red and Silurian genera. 
As far as the present evidence goes, this inference entirely breaks down, at 
least for those individuals that have come under our notice in the Survey 
Collection. The portions of limbs preserved can better be interpreted by com- 
parison with scorpion, and those with the bi-ungulate foot belonged to undoubted 
air-breathers. There is little doubt that the comb-like organs occupied the same 
position as those in scorpion, for they are constructed exactly on the same type. 
They have been found in the same position in Pterygotus, but attached to the 
under side of the lateral alee of the opercular plate, as shown by Woopwarp.* 
Professor GEIKIE has kindly placed at my disposal for study the specimen 
figured by Woopwarp, and which belongs to the Jermyn Street Collection. 
This plainly shows the gills in place. Woopwarp’s figures are in the main so 
truthful that it is unnecessary to make any new sketches to illustrate this paper. 
It may be as well, however, to say that what might be mistaken as the rachis of 
the left gill is in reality in a higher stratum than the gill filaments, and that the 
latter as seen on the specimen pass under it and reappear between it and the 
larger and unbroken and upturned portion of the left ala. The filaments are 
quite membranous and highly vascular, and well fitted to perform the function 
of breathing. In the Carboniferous combs, however, the filaments are not mem- 
branous, but are yet preserved as hard, tough, horny and elastic plates, so that it 
is improbable that they acted as gills, and the rachis is too thick and rounded 
ever to have been held beneath the thoracic plates. The rachis itself is in all 
probability the homologue of the lateral alz of the thoracic plates of Pterygotus 
and other older Eurypterids, while the “‘teeth,” so to speak, are the gill filaments 
chitinised and modified to perform some other function. 
The integument of the Carboniferous specimens examined are not crusta- 
cean in character, but are horny and like that of scorpions and insects. In 
* Mon. British Fossil Crust. belonging to the Order Merosomata, by Henry Woopwarp, LL.D., 
F.R.S., &c., p. 67, pl. xi. figs. 2a and 20, 
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