438 SAMUEL H. SCUDDER ON NEW 



as it does in Great Britain and, as will be seen by the following descriptions, from the 

 carboniferous deposits of Mazon Creek, 111. 



Xylobius frustulentus sp. nov. 

 PI. 37, figs. 4-G. 



This is a small species and represented by specimens closely resembling in general 

 apjiearance our smaller species of lulus from temperate regions. One is preserved on 

 a side view (fig. 5), strongly curved like a fish hook, and is apparently complete, thongh 

 both ends are rather obscure. It is long and vei-y slender, almost equal, tapering 

 scarcely in the least at either end and composed of alternately longer and shorter seg- 

 ments, as shown in fig. 6; the number cannot be determined from the obscurity of parts 

 of the body, but they would appear to number all told more than fifty. The larger 

 ones are about three, the smaller about foiir times as broad as long. The frustra are 

 the same on both, separated from each other by delicate incised lines, which are a little 

 sinuous as well as slightly oblique; they are very narrow, narrower than on any knoAvn 

 species, being eight or ten times longer than broad. The legs are delicate, slender, 

 cylindrical, a little shorter than the width of the body, the joints indeterminate. 



Length of the body, 33 mm.; width of same, 1.75 mm.; length of legs, 1.45 mm. 



This specimen, which comes from Mazon Creek, Avas received from Mr. R. D. Lacoe, 

 and is numbered 1812ab, in his cabinet. 



The second specimen (fig. 4), sent me after the preceding description was prepared, 

 is similarly preserved in a somewhat semicircular curve; as there, both ends are obscure 

 and probably neither of them is complete. It is long and slender, nearly equal but 

 slio'htly tapering on the posterior half and anterior fifth, and not so clearly composed 

 as there of alternate longer and shorter segments, the shorter, in the greater part of the 

 body at least, appearing more as mere interspaces and showing no sign of division 

 into frustra, which are perfectly evident and exactly as in the other specimen in the 

 shorter segments. The shorter segments have more the appearance of being originally 

 -formed of a less dense integument than the larger ones, and as being here folded or com- 

 X)re.-ssed; in this way only can the structure of the two specimens — which agree in all 

 other .respects — be made to accord sufficiently to consider them the same species. The 

 number of segments, counting only the larger ones, are twenty-nine, and they have 

 the same /Vjrm and proportions as in the other specimens, with exactly similar frusti-a. 

 The legs are of similar delicacy and length, but, as there, with indeterminate joints. 



Length ofbL>(1y, 31 mm.; width of same, 2.2 mm.; length of legs, 1.75 mm. 



This specimen -yvas obtained at Mazon Creek, and was received from Mr. J. C. Carr, 

 but is now in Mr. Lacoe's collection under the number 1812cd. 



Still another specimen from the same place has been more recently sent me by Mr. 

 "W. F. E. Gurley. I't is in better condition than the others, curled much as they, and 

 shows all but the very head and hinder extremity ; jirobably not half a dozen segments 

 are lacking; forty-one i-Dpeai'. These are alternately longer and shorter, one about one- 

 half longer than the otht.]-^ each with its own independent arching; the whole of a pair 

 of segments as thus constituted when seen on a side view, is about two-thirds as long 



