CARBONIFEROUS MYRIAPODA OF ILLINOIS. 425 



feature; the lateral spines extending on either side are fully as long as the width of the 

 body, sometimes considerably longer, and are remarkable for the great length and ine- 

 quality of the forks, at least from the fifth segment backward, the longer fork being 

 posterior and diverging from the other and sometimes as long as the stem of the spine 

 itself; there are, besides, basal thorns both anterior and posterior, of varying length but 

 the anterior usually the longer and sometimes very long and slender. The subdorsal row 

 of spines is clearly indicated by bosses (or pits in the obverse) upon most of the seg- 

 ments; the pleurodorsal series is not so clear, but appears to be indicated, posteriorly, 

 by the extremities of apparently simple sjjines which protrude laterally beyond the sides 

 of the body between the lateral spines. There is besides, protruding from the poste- 

 rior extremity of the sixth segment, just as I described it in A. major, a long slender 

 stiff rod, here thrust sidewise and thrown a little forward, longer than the width of the 

 body. 



The length of the specimen is 63 mm. 



The second specimen (fig. 4), received from Mr. Lacoe, under the number 1819cd, 

 shows only the posterior part of the animal and in an entirely different position. It is 

 preserved upon a side view, and shows about eighteen segments though only ten are 

 here figured. Here only the dorsal spines are shown, and they diff'er remarkably from 

 the others in being almost boot-shaped, the longer posterior fork being almost the only 

 one develojied; this is inclined at a strong angle with the stem, and is nearly as long as 

 it; moreover, the whole is short and stumpy, less than half as long as the width of the 

 tapering body, excepting on the posterior segments, and the anterior fork is only indi- 

 cated by a slight projection at the heel of the boot; as, however, they agree with those 

 of the lateral row in the other specimen (and not seen here) in the unequal length of 

 the forks, which mainly distinguishes either from A. major, they are placed together 

 until further light is obtained from other specimens. The legs are fairly well preserved, 

 are not closely crowded, slender, with only slight sign here and there of a median car- 

 ination, taper very regularly beyond the middle to a point, the last joint the shortest, 

 the preceding three subequal and only a little longer; at the hinder extremity of 

 the body they about equal in length the width of the body, but a dozen joints away, 

 while of the same length, the}^ do not more than equal half the breadth of the body. 

 The length of the fragment is 93 mm.; the legs are about 9 mm. long. The spines of 

 the other rows do not plainly appear, but their place is here and there obscurely in- 

 dicated. 



It remains to be seen whether we are here dealing with two species, but the complete 

 and striking inequality in the forks of the spines will not allow us to look on them as 

 belonging to A. major, to which at first sight they have a striking resemblance. Neither 

 of these specimens indicates quite so large a species as that, though much stouter than 

 any species of Euphoberia. 



Mazon Creek, 111. 



Euphoberia Meek and Worthen. 

 I subjoin a table of the species of this genus known up to the present time in North 

 America. 



MEMOIRS BOSTON SOC. NAT. HIST., VOL IV. 67 



