452 SAMUEL H. SCUDDER ON THE 



the abdomen are clistinct and not voundcd, and the first course of the Uiteral slope as the 

 abdomen enlarj^es is in exact continuation of the direction of the anterior half of the sides 

 of the ccphalothorax; tlie abdomen widens to beyond its middle, so as to be half as broad 

 again as the cephalothorax, and then narrows, the outline of its apical half being an al- 

 most exact semicircle with the central point of the abdomen (near the middle of the fifth 

 segment) for its centre. A scalariform incised line runs on either side obliquely in- 

 ward from opposite the outer limits of the cephalothorax to either side of and in close 

 proximity to the large circular or more often transversely oval anus, dividing the body 

 into three subequal longitudinal thirds and giving it a trilobitic aspect, which is more 

 pronounced from the fact that the central region is nearly flat or only slightly domed, 

 while the sides fall oif as far as the again flat, lateral flanges; these are separated about 

 as distinctly from the rest of the body by an incised line subparallel to the margin and 

 dividing the lateral lobes as a whole into nearly equal halves, extending also across the 

 middle of the seventh segment and dividing it just beyond the anus into an anterior and 

 postei'ior half. 



The entire surface of both cephalothorax and abdomen is delicately, uniformly, and 

 rather sparsely granulate. In the original description it was described as punctate, but 

 this is apparently a mistake, the surface being punctate only in casts, though it is diffi- 

 cult in the flattened condition of all the specimens to speak confidently. 



Length of cei)halothorax, .5.25 mm.; its greatest width, (5.75-7.5 mm.; width at poste- 

 rior extremity, 1.5-5.5 mm.; length of abdomen, 8-12.5; width at base, 5.75-8.25 mm.; at 

 widest point, 8-12.5 mm. 



The specimens were found on a dark gray carbonaceous shale associated with fei-ns, 

 in the subconglomerate coal measiu'es six miles northeast of Fayetteville, Ark., by Prof. 

 F. L. Harvey of Fayetteville. Some of the specimens are in Mr. R. D. Lacoe's collec- 

 tion under the number 1753. 



Anthracomartus pustulatus. 



PI. 40, figs. 5, 8. 



A.nthracoma7'tus p'iistulatus Scudd., Pi'oc. Amer. Acad. Arts Sc, xx, 18 (1884). 



The stone on which the single known specimen occiu-s is broken just at the front edge 

 of the cej^halothorax, as is shown by the course of the front pairs of legs and of the pal- 

 pi in the face of the broken wall (fig. 5). If this break has not interfered, as looks pos- 

 sible, with a projecting front, the cephalothorax was squarely ti'uncated in front and was 

 of a quadrate form, narrowei-, however, in fi-ont than behind and with tolerably straight 

 sides, the hind margin straight or a little concave. The surface of the cejjhalothorax is 

 however the most remarkable thing about it, the sides being strongly elevated, and the 

 middle third deeply sunken in a longitudinal furrow rapidly widening posteriorly, from 

 the bottom of which a sharp median ridge arises with abrupt sides, gradually increasing 

 in elevation and thickness from the middle of the front half where it arises, to the middle 

 of the hinder half where it abruptly terminates, but nowhere rising to half the height of 

 the sides. The abdomen on the contrai-y is strongly arched, the central field somewhat 

 flattened and separated from the lateral by distinct carinae. The outline of the abdomen, 



