74 



TERRESTRIAL CARBONIFEROUS ARACHNIDA. 



The coxas of the five pairs of post-oral appendages radiate round the elongated 

 sternal area of the prosoma, which is about twice as long as wide. Of the first 

 pair of appendages or chelicerae no details can be determined. Those of the second 

 pair, the first post-oral appendages or palpi, are normally constructed and pediform, 

 consisting of six segments ; the remaining pairs are similar in form and segmenta- 

 tion and approximately similar in size, each consisting of the usual number of 



seven segments.' 



Type Species. — Trigonotarbus johnsoni, sp. nov. 



Although in the structure of its carapace this genus presents greater resem- 

 blance to Anthracomarlus than to Eopliri/nus, it approaches much nearer to the 

 latter than to the former in the structure of the sternal plates of the opisthosoma, 

 especially of those in the region of the generative orifice. It also resembles 



-KZy 



d. 



Fig. 38. — Trigonotarbus johnsoni, yen. et sp. n. ; restoration from several specimens, about six times nat. 

 size.- Coal Measures ; Coseley, near Dudley, a., dorsal surface with appendages; b., lateral view of 

 carapace, about eight times nat. size ; c, ventral surface ; d., transverse section of the opisthosoma to 

 show the convexity of the ventral surface and the uptilted pleura?. 



Eophrgnus in having the laminae of this region undivided on the dorsal side, and 

 not differentiated by a sulcus from the rest of the sternal plates on the sternal 

 side of the opisthosoma. No doubt its nearest known ally is Anthracosiro, of 

 which the sternal surface of the opisthosoma is unknown ; but Trigonotarbus is 

 certainly generically distinguishable by the shape of the carapace and of the 

 laminee of the opisthosoma, and by the absence of lateral constriction between the 

 prosoma and opisthosoma. 



Trigonotarbus johnsoni, sp. nov. Plate III, fig. 4; Text-figure 38. 



Integument closely and tolerably uniformly granular. Carapace about as long 

 as its own posterior width, and a little longer than the anterior six terga of the 

 opisthosoma. Opisthosoma a little longer than wide ; the terga subequal in length 



