62 TERRESTRIAL CARBONIFEROUS ARACHNIDA. 



upwards to the inner edges of the pleural plates, the pleural plates themselves 

 lying more in a horizontal })lane. When directed backwards the fourth leg lies 

 apparently in the space beneath the pleural plates and against the upsloping external 

 area of the ventral surface. In front of the first sternal plate, and between it and 

 the sternum of the prosoma, with the coxce of the legs of the last pair on each side, 

 there is a longer or shorter area which was [)robably membranous. This, perhaps, 

 represents the sternal region of the pre-genital segment, which seems to be 

 unrepresented on the dorsal side of the opisthosoma. The sulcus on the dorsal 

 side, which cuts the laminae into two moieties, is represented on the sternal side by 

 a similar sulcus following the curvature of the lateral and posterior borders of the 

 opisthosoma. 



I believe the above-given interpretation of the ventral surface of the opistho- 

 soma to be, approximately at all events, correct. But in no specimen that I have 

 seen is the ventral surface exposed fully from below. In every case where the 

 sternal plates are well shown it is their inner surface that is exposed — that is to 

 say, the organism is S})lit in two in such a way that the dorsal area is seen from 

 below and the ventral area from above. Hence in my description of the ventral 

 skeletal plates I have interpreted grooves and hollows as ridges and elevations 

 respectively, and vice-verHd. This opens up possibilities of error which must not 

 be lost sight of; and when discussing Pruim/(/ale and Anthracomartv^i in the 

 November issue of the Geological Magazine for 1910, I inadvertently fell into the 

 error of describing a deep groove on each side of the lower surface of the opistho- 

 soma. The structure should have been described as a ridge. 



The Anthracomartidse are sharply distinguished from the Eophrynida? and 

 from the Anthracosironida3, as exemplified respectively by Eophrijnns and Trujono- 

 tarhua, not only by the structure of the anterior sternal plates of the opisthosoma, 

 but also apparently by the separation of the pleural plates into an outer and an inner 

 moiety by sulci, which are apparent upon the ventral as well as upon the dorsal 

 surfaces. They further differ from the Eoplirynida3, but not from the Anthraco- 

 sironidae, by the structure of the carapace of the prosoma. 



Genus ANTHRACOMARTUS, Karsch (emend.). 



1882. AnthracomartHs, F. Karacli, Zeitsclir. deutscli. geol. Ges , vol. xxxiv, p. 55G. 



188.'3. Anthracomartiis, S. H. Scudder, Proc. Amer. Acad. Arts Soi., vol. xx, p. 17. 



1890. Anthracomartiis, E. Haase, Zeitsclir. deutscli. geol. Ges., vol. xlii, p. G45. 



1901. Proui)j(jale, A. Fritscli, Fauna der Gaskolile, vol. iv, p. 58. 



1902. Anthracomartiis, R. I. Pocock, Geol. Mag. [4], vol. ix, p. 491. 

 1904. Anthracomartus, A. Fritsch, Palaeoz. Araclm., p. 36. 



1904. Promijijale, A. Fritsch, Palaeoz. Araclm., p. 19. 



1910. Anthracomartus, E. I. Pocock, Geol. Mag. [5j, vol. vii, pp. 504 — 508. 



