110 HT, Woodward—Eurypterus lanceolatus. 
articulations in the swimming-feet as well as in their general 
form. The intercalated plate and minute terminal palette, well 
seen in &. lanceolatus, are peculiar to this genus. ‘There are 
certainly eight articulations in the antenmules: but I cannot 
positively discern a ninth. 
The lateral lobes of the thoracic plate in this species are 
much deeper, in proportion to the central double appendage, 
and the two intercalated plates are larger, than in the American 
Huryptert. The line of division between the pair of central 
organs is continued much higher up; and they are divided 
near their terminations into three joints, as seen in the figure 
CRIN, fie '8iz): 
The entire surface of the thoracic plate is closely covered 
with the minute scale-like markings, or wrinkles, peculiar to 
this group, which are also observable upon the anterior half of 
each thoracic seement, the abdominal segments beimg smooth 
and free from all ornamentation. 
There seems no reason to doubt the homology of this (tho- 
racic) plate with the leaf-like appendage of Limulus, as pointed 
out by Professors Hall and Agassiz (op. cit.), and still more 
strongly confirmed by Professor Huxley, in his lectures on 
the anatomy of Limulus (part of his course of ‘ Lectures on 
General Natural History,’ published in the ‘ Medical Times and 
Gazette’ for 1857), in which he has demonstrated it to be a 
thoracic and not an abdominal appendage, as it might at first 
sight be considered. This thoracic plate in Limulus, which 
bears the reproductive organs upon its inner surface, overlaps 
in great measure the five corresponding and succeeding abdo- 
minal lamelle, which cover and sustain the branchiw. We have 
no indication of branchie in the Kurypteride, although it is 
quite certain that these must have existed. Peculiar and 
delicate striated markings have been observed upon and near 
the thoracic plate in Slimonia acuminata;* and it is highly 
probable that this plate covered both the branchiz and the re- 
productive organs. 
I have been unable to detect the larval eye-spots which are 
seen so clearly in the American Kurypteri and in some of the 
Pterygoti also. 
There is without doubt an affinity between the genera 
Eurypterus and Slimonia. The latter approaches the former 
and recedes from Pterygotus proper, not only in the absence of 
chelate appendages, but also in the more narrow and elongated 
* J shall have occasion to refer to this species again in a future paper; but I 
may state that more than one plate is now known “to have been attached to the 
thorax of Slimonia. 
