MR. LUBBOCK ON THE THYSANURA. 
51V.) 
claw, five or six small teeth ; the lesser claw is lanceolate in form, but with the lower 
margin straighter than the upper one, and has a single, very minute tooth on the upper 
side. The second and third pairs of feet much resemble the first ; but the small spine 
on the lesser claw of the third pair is rudimentary or altogether absent. On the bit si 1 
part of the caudal appendage are, as in M. plumbea, nine black spines. In that species, 
however, they are simple and short, while in the present they are much longer. The 
four first form a somewhat curved line ; the remaining five are arranged in a straight 
row, and have small processes at the side ; the apical spine and the penultimate arc the 
largest. 
The form and arrangement of these spines, and the structure of the feet, satisfactorily 
distinguish this species from the preceding. If in 3L minor, which is smaller than 
M. plumbea, these caudal spines had been smaller than in that species, and the spines on 
the feet had been less numerous, we might well have supposed that these differences 
depended on age, and were therefore of no vaiue as specific characters. I was, indeed, 
for a long time disposed to consider M. minor as being merely the young stage of the 
larger M. plumbea; but the large specimens are comparatively so rare, that, for this 
reason alone, such an opinion seemed to me untenable. This is, I think, confirmed by 
the structure of the feet and of the caudal appendage. 
"With the specimens above described are others which are narrower, and, without the 
scales, of a yellow colour. When placed in spirits, also, these two forms behave dif- 
ferently; the first swell, and the intersegmental membranes are more or less exposed, 
while the other variety retain their original form. The structure of the antenna?, the 
feet, and the caudal appendages is, however, so similar in the two forms, that I do not 
feel justified in separating them specifically. 
Lepidocyettjs. 
Lepidocyrtus argentatus, Bourlet ? (PI. LIX. figs. 16, 17.) Body cylindrical, the third 
segment decidedly narrower than the second and fourth ; silvery, with brilliant me- 
tallic reflexions. Eyes situate on a black patch. Antennae and legs grey, the latter 
paler than the former; basal segment of antenna short, second and third equal, 
and about two-thirds as long as the apical. Caudal appendage pale, reaching to 
the ventral tube. Thorax with a tuft of short hairs in front ; posterior segments of 
abdomen with long, scattered setae, some of which are waved. 
Length ^th of an inch 
Occurs all through the winter, from November, and perhaps earlier, to April, under 
logs of wood in Kent. g 
The mandibles have respectively four and five teeth. The labrum is pear-shaped. 
The feet have each a single tenent hair of the usual form. The large claw has two small 
teeth on its under side. The small claw is lanceolate. The first abdominal segment is 
decidedly narrower than those on each side of it. 
It may well be doubted whether this is really the L. argentatus of Bourlet, his descrip- 
tion being very brief and unsatisfactory. He says, « Thorace minus elato, corpore squamis 
VOL. XXIII. 
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