CARBONIFEROUS ARACHNIDA OF NORTH AMERICA. 447 



next three segments are larger and longer, subequal, bnt each a little longer than the 

 IDreceding, snbmoniliform, being largest apically, the angles rather sqnare; the sixth joint 

 is as long as the fifth but slenderer and equal, while the seventh is a mere rapidly taper- 

 ing bluntly pointed cap to the sixth. The surface of all bnt the last three joints is flat 

 or equally rounded, Avhile these terminal joints have a common median ridge of consid- 

 erable strength. As preserved, there is next the anterior margin a very deep rounded 

 groove occupying nearly half the width of the joint; the opposite margin has also a pro- 

 nounced but narrow groove and between them is a high rounded ridge, narrower than the 

 first mentioned groove, terminating in the middle of the last joint where the lateral 

 grooves join; they are slender. From the single fragment of one of the anterior pairs 

 of legs that remains, apparently of the fifth joint, these were scarcely stouter; but the 

 hinder pairs are twice as stout, and very heavily punctate; of the third ])air the first 

 four joints ai-e preserved in whole or in part upon either side. The first joint is too oli- 

 scure for description ; it can only be said to have been small, and probably of the same 

 size and pei-haps of the same form as the second which is quadrate (it is only seen pei-- 

 fectly upon one side), about twice as long as broad; the third joint is of similar form but 

 longer and perhaps slightly broader at its distal than its basal extremity; it is half as long 

 again as the preceding joint, and is followed by a fourth joint exactly like itself; all the 

 joints of this leg, with the possible exception of the basal, are heavily ridged as in the 

 front legs but not so conspicuously. Of the fourth pair of legs only what are perhaps the 

 third and fourth joints remain (and not completely) ; if they are these joints they agree 

 altogether with those of the third pair of legs. The distinction in size between the base 

 and apex of the joints of all the legs has been exaggerated by the artist. 



Length of the body, 19 mm.; breadth of same, 9.5 mm.; length of median furrow, 6 

 mm. ; last three abdominal segments, 6 mm. ; palpi, 11 mm. ; breadth of same, 5 mm. ; length 

 of third joints of third pair of legs, 2.5 mm.; breadth of same, 1 mm. 



This description was originally drawn up from a single specimen from Mazon Creek, 

 submitted to me by Mr. R. D. Lacoe under the number ITOlab. Since it was wi'itten, 

 the same gentleman has sent me four more specimens from the same locality all of which 

 are believed to belong here, although they range in size from 16.5 mm. to 21 mm. in 

 length and from 8 mm. to 11 mm. in breadth. In one of them, No. ITOlcd (fig. 1), 

 the legs are unusually well preserved, one in particular, apparently the third pair, being 

 nearly complete, showing nearly the whole of five joints, the terminal being simply point- 

 ed, and their size, counting from the tip, being as follows: first or terminal joint, length, 

 1.85 mm., breadth at base, 1 mm.; second, length, 2.2 mm., breadth at base, 1.5 mm.; third, 

 length, 2.2 mm., breadth at base, 2 mm. ; fourth, length, 2.1 mm., breadth at base, 2.1 

 mm. ; fifth, length, 2 mm. The fourth pair of legs is slightly longer. 



GeKATARBUS gen. nOV. (j-7,paq, TdplSo<;) 



Cephalothorax suborbicular, the front rounded or very broadly angulate, about half 

 as large as the abdomen, or a little more than that, but either distinctly narrower than 

 the abdomen or separated from it by a marked lateral constriction. Coxae radiating from 

 a short median line, which apparently lies at the bottom of a shallow central pit. Legs 



