440 SCUDDER ON CARBONIFEROUS MYRIAPODA. 



and may extend beyond the liniits of the enclosing nodnle. The body is of nearly uni- 

 form width, but tapers forward a very little on the first eight or nine segments and 

 toward the posterior end. The segments preserved are forty in number, and are of 

 about the same proportion as in the other specimen. From its better preservation, how- 

 ever, it shows clearly, what the other shows but vaguely, the exact form of the segments; 

 the body was plainly cylindrical or neai'ly so, and the anterior and postei-ior border of 

 each segment was thickened to form together an elevated, more or less rounded band, 

 together a little more than twice as broad as the intermediate, lower and more flattened 

 interspace covering the most of the segment; the anterior thickening occupies twice as 

 much of the band as the posterior; the sutures of the frustra cross the entire segment, 

 including the band, both antei-iorly and posteriorly; the frustra are separated and marked 

 oft' by slight raised lines, running with a slight ol)liquity and are of the same propoi'tion 

 as in the other specimen. The head shows no peculiarities, as it merely ends in a blunt- 

 ly rounded curve, with no visible appendages and is altogether very obscure. The legs 

 are delicate, slender, cylindrical, pointed, and unless in the proportionate lengths of the 

 joints, which cannot be determined, in all respects like those of a modern lulus; they 

 are nearly as long as the width of the body. 



This specimen is also of special interest from the fact that its excellent preservation 

 ensures seeing any spines which might project beyond the body, and which do not exist. 

 On one of the stones, however, there may be seen on most of the segments a minute 

 Avart or tubercle centrally placed, forming a pleurodorsal row apparently about midway 

 between the middle of the sides and the middle of the back, similar therefore to some 

 obscure "indications of the same sort on other species of Xylobius. It is interesting also 

 as showing clearly the lower edges of some of the dorsal shields next the present lower 

 edge of the fossil, showing that here the ventral scutes must be much narrower than 

 the dorsal. 



The length of the specimen is 45 mm.; its breadth in the middle, 4.5 mm.; at the 

 head end, 4 mm.; length of legs, 4 mm.; their greatest breadth, 0.08 mm. 



Both the specimens are from Mazon Creek, 111. 



The species differs from any known by its much larger size, the narrowness of its 

 frustra, and the strap-like character of its sutural prominences, which do not fall grad- 

 ually to the level of the lower part of the segment forming a more or less striking selli- 

 form curve, but abruptly. 



EXPLANATION OF THE PLATES. 

 Plate 33. 

 Eigs. 1 and 3 are by Mrs. Katheriue Peirson Eamsay ; figs. 2 and 4 by J. II. Emerton. 

 Euphnberia hystricosa |. 

 Acantherpestes infqualis ^. 

 Enphoheria hystricosa ] ; reverse of fig. 1. 

 Acantherpestes iuequalis -}. 



Plate 34. 

 Figs. 1, 3 and 7 are by Mrs. Katherine Peirson Ramsay; tlie others by J. II. Emerton. 

 Fig. ■ 1. Enphoheria spinulosa f. 



Fig. 2. Enphoheria armigera ; a portion of tlie integument of one of tlie neigliboriug segments of fig. 8, furtlicr en- 

 larged. 



