Paleocampa, Meek and Worthen. 287 
spreading bunches of very densely packed, stiff, slender, 
bluntly tipped, rod-like spines, a little longer than the legs. 
The bunches are seated on mamille and arranged in dorso- 
pleural and lateral rows. 
The individual rods have an intricate structure: istead of 
being striate, as supposed by Meek and Worthen in their last 
examination, they are furnished externally with about eigh- 
teen longitudinal equidistant ridges, about half as high as 
their distance apart ; the edges of these ridges are broken into 
slight serrations at regular intervals about equal to the dis- 
tance between neighbouring ridges, the highest point of each 
serration being towards the apex of the spine ; the body of 
the ridge itself appears as if broken at each serration. The 
intervening space between neighbouring ridges is equally 
divided by two or three exactly similar but minute ridges, 
serrated at more frequent intervals. This serration of both 
larger and smaller ridges, with the apparent jointing or inci- 
sion of the ridges to the base at the lowest point of each 
serration, gives the whole spine a jointed appearance; but a 
close inspection of the floor of the spine itself between the 
ridges shows no sign whatever of any break in its perfectly 
smooth surface. ‘The diameter of the spines is only about 
one tenth of a millimetre; and yet it gives room for an 
exquisitely regular division of its periphery by seventy or 
more delicate ridges, every fourth one higher than the inter- 
vening, and all broken at minute intervals by uniform serra- 
tions. The preservation of these structures from Carbonife- 
rous times is only less remarkable than the occurrence, 
apparently so near the origin of the type to which it belongs, 
ot ornamentation of such excessive delicacy, finish, complica-: 
tion, and regularity. I cannot discover that dermal appen- 
dages of such delicate and specialized organization occur any- 
where today among arthropods, unless it be when developed 
as scales, as in Lepidoptera and occasionally in other groups 
of hexapods. Some cheetopod worms have indeed hairs of 
curious asymmetrical structure, often very delicate and some- 
what specialized, but never, so far as I can learn, to nearly 
so high a degree as here. ‘The collection of these rods into 
fascicles is also not a little curious, and is again a feature 
known now in arthropods only in a few instances, such as 
some tufts of hairs in lepidopterous caterpillars like Orgya, or 
the pencils of hair-like scales im the males of some perfect 
Lepidoptera (e.g. at the tip of the abdomen in Heliconia, 
Danais, Agrotis, Leucarctia, &c.), or in the terminal fascicles 
of barbed hairs in the myriopodan genus Polyxenus. 
There is no group of animals into which such a jointed 
