FROM THE CARBONIFEROUS FORMATION. 163 



the length is barely 2 mm. The segments although much flattened in preservation sho.v, 

 particularly in the larger parts of the body, distinct signs of having been ridged on the 

 anterior half which bears the spines, a feature not seen, where we should the more expect 

 it, in the figures given of the lateral views of the two other specimens. 



The head is delicately granulated, the granules oblong with their longer axes longitu- 

 dinal, and showing a tendency to run together in wavy but generally straight longitudinal 

 ridges ; these markings however are rather faint and dull ; similar granulation appears 

 obscurely in one or two of the segments behind the head, but shows no tendency to a long- 

 itudinal arrangement. The same circular disks which were described in the large sjieci- 

 men of Acantherpestes major appear here also all over the body, but the material of which 

 they are formed has generally cracked extensively in an irregular manner, so that they 

 are not so conspicuous ; those of average size have a diameter of about 0.35 mm. 



The subdorsal row of spines appears only by the little pits upon the surface, which show 

 that these rows are placed a little nearer together than either of them to the lateral rows. 

 The spines (PI. 12, fig. 2) are preserved in the lateral rows on one side nearly throughout 

 the body, on the other in the anterior third ; in their length they show a constant relation 

 to the size of the segments, and are present on all the segments behind the head, excep- 

 ting near the tail where they are lost. They are more than half as long as the segments 

 on which they occur, very broad at base, rapidly narrowing at first, especially on the hinder 

 edge, and then taper gently, with a slight backward curve, to a delicate pointed tip ; thev 

 are not compressed or depressed but circular in cross section, and bear at the base posteri- 

 orly (only seen in this specimen on one side of the body) a posterior, basal, triangular thorn 

 directed backward and outward ; it is stout, conical, pointed and nearly half as long as 

 the segments ; its absence from the spines of the right side is due no doubt to the position 

 of these spines, and the spinules might be found attached also to them by cutting the 

 stone ; besides this basal posterior thorn, there is an anterior delicate spinule on the 

 middle of the spine plainly visible, at the base of which the spine has a slight bend back- 

 ward in most cases ; this is not shown in the one selected for enlargement (PI. 12, fig. 2), 

 nor is it brought out in the drawing of the natural size ; from certain appearances it looks as 

 if there were, at the point where this anterior spinule arises, not merely this one spinule, but 

 a circlet of them, three x>v, counting the extremity of the spine as one, four in number : one 

 anterior as described, minute, pointed, hardly directed forward ; the posterior or spine 

 proper, which is nearly as long as the basal part of the spine, tapering regularly and 

 pointed, directed only a little backward, divergent from the first at an angle of about 45°, 

 and occasionally very slightly curved backward ; still another superior (or interior) one 

 is indicated by a slight mark, seen in the enlarged drawing as a dark spot at the base of 

 the anterior spinule, indicating the base of a spinule ; and ]jossibly, to match it, one on the 

 opposite side, of which of course no indication could well appear. 



The only appearance of legs is in a short fragment at the middle of one side which slopes 

 down toward the body, where three sets of two each appear ; they are of equal length, 

 and therefore are probably complete, for the stone is not split on a different plane from 

 that in which they lie until some distance beyond their extremities ; they are therefore 

 very much shorter than in Acantherpestes major and considerably shorter than the width 

 of the body; the first joint appears to be broken off at the edge of the stone; the second 



