CARBONIFEROUS MYRIAPODA OF ILLINOIS. 421 



Length of fragment if extended, 48 mm.; breadth of head, 6.4 mm.; greatest breadth 

 of body, 8 mm. 



Eileticus aequalis sp. iiov. 

 PI. 38, figs. 6-9. 



A second species seems to be indicated by a couple of specimens from the same local- 

 ity sent me by Mr. Lacoe nnder the numbers 1836ab and 1836cd, both shown in obverse 

 and reverse. The better of these (figs. 6-8) is a remarkably well-preserved but very 

 fragmentary specimen, showing the dorsal view of the front part of the body consisting 

 of the head and eleven segments. The head closely resembles that of the sjDecimen of 

 the last species just described, but has more accentuated sulcations both longitudinal and 

 ti-ansverse, and the foot-jaws are more pronounced even than there; as there, also, the 

 front of the head is broken, but on the reverse, what appear to be the first two joints of 

 an enormous antenna project laterally, in which case the antennae are broader at the base 

 than the very base of the foot-jaws. 



The segments of the body have a smooth texture, and the same transverse stepped 

 sulcation that occurs in the preceding, but with less jirominent edges; still it differs from 

 it markedly in that the segments are almost absolutely uniform in size; they have a late- 

 ral depressed and horizontal flange with a rounded edge, while the main body is strong- 

 ly arched, and the lateral flange bears such slight tuberculations as can be seen; without 

 this flange the body is slightly narrower than the head; with it a little wider; the seg- 

 ments without the flange are a little more than three times as broad as long. 



Length of fragment, 26.5 mm.; of one of the piincipal segments, 2.3 mm.; breadth 

 without flange, 7.25 mm.; with it, 10 mm.; breadth of head, 7.75 mm. 



The other specimen (fig. 9) is similarly preserved but more imperfect, one whole side 

 being broken, and the head far less complete. There is little to be said about it, but its 

 transverse arching shows that it was nearly cylindrical; and the posterior as well, but 

 not to the same extent, as the anterior margin of the segments has a stej^ped transverse 

 sulcation. The head is far less perfect, but as far as it goes shows precisely the same 

 featiu'es; the body segments are thirteen in number, and show by their apparent inequal- 

 ity in length that there was greater or less power of extension by elastic intersegmental 

 membranes. No one of the segments is perfect, so that the proportions cannot be stated, 

 and only one side is approximately perfect, and that does not preserve the lateral flanges; 

 but enough remains to show that the specimen by its equality of breadth belongs to this 

 rather than to the preceding species. 



Length, 50 mm. ; breadth of head, 7 mm. 



Palenarthrus gen. nov. (-«'-!«!, i^apOp<:z) 



A genus evidently very diflerent from anything before known from the carboniferous 



rocks, but unfortiinately known only by a single specimen, which from its incompleteness 



leaves much to be desired. That it was a scolopendriform chilopod or archaic type of 



chilopod is evident from the flattened rectangular plates of which the dorsal surface of 



