OF ARTS AND SCIENCES. 15 



forms enables me to supplement, and, as I believe, to improve these, 

 and accordingly the following systematic sketch of paleozoic Arach- 

 nida has been prepared, into which have been thrown such suggestions 

 and new facts as have come to hand. 



Order ANTHRACOMARTI Karsch. 



Body more or less depressed, the cephalothorax and abdomen dis- 

 tinctly separable. Ceplialothorax frequently made up in large part of 

 pedigerous segments more or less wedge-shaped, and visible ai)ove as 

 well as below, the arrangement of wliich corresponds to that of the 

 coxae. The abdomen forms a single mass, and is composed of a 

 variable number of visible segments, ranging from four to nine. 

 Palpi not much longer than the legs, simply terminated. 



Fara. ARTHROLYCOSID^. Harger. 



Cephalothorax orl)icular, twice as large as the abdomen. Coxre 

 radiating from a central pit. Abdomeu oval, much narrower at base 

 than the cephalothorax, with no longitudinal sculpturing, and com- 

 posed of seven segments. No abdominal appendages. 



Arthroltcosa Ilarger. 



Arthrolycosa antiqua Harger, Amer. Journ. Sc. Arts, (3,) vii. 219- 

 223 (fig.), 1874. Mazon Creek, Illinois. 



In his description of tliis arachnid, Ilarger inclines to the belief that 

 the terminal segment of the palpus is chelate. He says (loc. cit.) : 

 " The third [joint] is broken near its 2:)roximal articulation, and the 

 connection of this appendage with what seems to be its distal cheliform 

 segment is unfortunately imperfect. This segment is also poorly pre- 

 served, and the articulation of its digit is only to be seen with a good 

 magnifier and in a certain light. ... I do not, however, consider the 

 forcipiilate character of this segment beyond a doubt. It is jierhaps 

 not improbable that it may have been modified much as in the males 

 of ordinary spiders, and not truly forcipulate." 



Having reason, by its undoubted relationship to other forms of 

 Anthracomarti, to doubt the forcipulate character of the palpus, of 

 which Harger speaks so doubtfully. Professor Marsh kindly permitted 

 me to study the type in Yale College Museum, and I find on close 

 examination that not only is the joint in question not chelate, but it 

 terminates by a straight, transverse suture, and is followed by a por- 

 tion of another, apparently short, terminal joint. 



