ARTHROLYCOSA. 35 



impression just in front of the posterior border. Faint indications of the 

 basal segments of the legs are traceable on one side, no trace of the coxa? 

 or sternal area of the prosoma being observable. The opisthosoma is wide, 

 with its lateral and posterior borders strongly rounded ; it is markedly narrowed 

 in front and is distinctly segmented on its dorsal area, the terga extending across 

 the Avhole width of this region from side to side. Of the segmentation of the 

 greater part of the ventral surface I can affirm nothing with certainty except as 

 regards the posterior extremity, where two annuliform segments surround the 

 last or anal segment. The latter, as I interpret the fossil, consists of a transversely 

 subelliptical tergal plate and of a crescentic sternal plate. 



Fig. 10. — ? Arthrolycosa, sp. — Coal Measures ; Coseley, near Dudley. Wheelton Hind Collection, a, dorsal 

 surface of carapace and of opisthosoma, the posterior segments of the latter showing through the 

 overlying last tergal plate visible on the dorsal side, about four times nat. size; b, terminal 

 segments of the opisthosoma, about six times nat. size. 



Approximate length and width of carapace 4 mm. ; length of opisthosoma 

 G mm.; with 5"5 mm. or possibly less, if this region is expanded by crushing. 



Coseley, near Dudley. 



The morphological interest of this specimen lies principally in the structure of 

 the posterior segments of the opisthosoma, which are unlike those of all recent 

 Araneas in being annuliform and firmly chitinised. In this character the fossil 

 shows a nearer approach to the Peclipalpi, serving in a measure to bridge the 

 interval between these two orders, which are admittedly related to one another. 

 No trace of spinning appendages is to be seen. If they had been close to the anus, 

 as in all recent Spiders except Liphidvus, indication of this would probably have 

 been preserved. Hence it may be supposed that they were situated somewhere 

 near the middle of the ventral surface as in the last-named genus. 



