222 C. E. Beecher — Arthrolycosa antiqua. 



and in addition, the last somite shows a depressed central area 

 which may correspond to the spinneret, but otherwise, no 

 abdominal appendages can be detected. The longitudinal lines 

 represented in the figure have been produced by the folding of 

 the test, due to compression in the rock. 



Considerable interest is attached to the position and associa- 

 tion of the specimen. From the figure and profile, it is seen 

 that all the elements of the spider are in nearly their natural 

 position, having undergone but slight distortion, while its per- 

 fection indicates that it is not a shed skin which is preserved, 

 but that the actual animal was entombed. 



In the same concretion are fragments of the broad leaves of 

 a rush-like plant, and it is not improbable that they furnished 

 a float upon which the spider was carried out from the land so 

 that its remains are found mingled in the same beds with 

 marine organisms. 



With the additional evidence furnished by the original speci- 

 men, the systematic position of this form is open to revision. 



It has been generally recognized as the type of a new family, 

 Arthrolycosidse, as first established by Mr. Harger. Professor 

 Scudder placed this family at the beginning of the order An- 

 thracomarti. The characters of the order as enumerated by 

 him are : " Body somewhat depressed, the cephalothorax and 

 abdomen distinctly separable. Cephalothorax usually made up 

 in large part of more or less wedge-shaped pedigerous segments, 

 the arrangement of which corresponds to that of the coxae. 

 Abdomen forming a single mass and composed of from four to 

 nine distinct joints. Palju not much longer than the legs and 

 simply terminated."* 



With the exception of Arthrolycosa, all the families of this 

 order comprise species which have the abdomen larger than 

 the cephalothorax, and divided longitudinally into well defined 

 areas. The cephalothorax is composed of distinct wedge-shaped 

 pedigerous segments, while in Arthrolycosa, it is formed of a 

 single piece, not more divided into coxal elements than in the 

 living species of Tetrapneumones. 



The palpi of the Anthracomarti are said to be " not much 

 longer than the legs," and, in this respect, Arthrolycosa differs 

 in having short stout palpi, about twice as long as the man- 

 dibles, and reaching to the fourth segment of the anterior legs. 

 The arrangement of the eyes and mandibles is also quite dis- 

 tinct in the two groups. 



On account of these important differences, it seems necessary 

 to exclude the genus from the order Anthracomarti, and at 

 present, a strict interpretation of any of the orders will not ad- 

 mit this form. 



* Bulletin U. S. Geol. Surv. No. 31, Systematic review of our present knowledge 

 of fossil insects, including Myriapods and Arachnids. Washington, 1886. 



