56 TERRESTRIAL CARBONIFEROUS ARACHNIDA. 



1902-3. Aiithraconiarii, K. I. Pocock (sensn tttricto). 



1904. PlenroraiHw, A. Fritscli fas Suborder of Araiiese). 



1904. Meridoijaiiira (= Anthracomarti), A. Friiscli fin part as Suborder of Opiliones). 



Prosonia covered dorsally ])y a carapace consisting of a single plate, variable in 

 form, but very generally marked ])osteriorly with a transverse groove indicating 

 the line of fusion between the tergal plate of the sixth somite and those of the 

 preceding five. No movable plate in front overhanging the chelicera^. Eyes, when 

 traceable, two in number. 



Appendages of the first pair (chelicerae) unknown. Those of the second pair 

 (palpi) simple and pediform and consisting of six segments ; those of the remaining 

 four pairs similar in form, andjulatory in function, and consisting of seven segments. 

 The basal segments or coxa? of the palpi and ambulatory limbs, /. r. of the five pairs 

 of post-oral appendages, large, triangularly wedge-shaped, but movaljle and arranged 

 round the narrower or wider sternal area, which was furnished with a median 

 elongate sternal sclerite. Mouth-parts unknown. 



Opisthosoma Avithout appendages, movably jointed to the prosoma, 1)ut with its 

 individual segments apparently welded together, though the sutural lines persist. 

 Seven tergal plates are always traceable on the dorsal side, the first of the seven 

 (r. e. the seventh counting forwards from the posterior end) being almost invariably 

 longer than those that succeed it ; each tergum is marked on each side with a 

 longitudinal sulcus or groove which separates a lateral lamina from the median 

 area of the tergum ; sometimes there is a second sulcus nearer the external 

 margin than the one just mentioned; hence each tergum is divided into either 

 three or five distinct areas according to the number of sulci. In front of the 

 seventh tergum from the end, either one or more tergal sclerites may be traced ; 

 these are usually not provided with lateral laminae and may be overlapped more 

 or less by the posterior border of the carapace ; they appear to represent from one 

 to three additional tergal plates undergoing excalation. The last tergal plate on 

 the dorsal side, that is to say the seventh, not counting the variable number of 

 anterior tergal plates just mentioned, is the narrowest of the series; but it is almost 

 invariably provided with an unpaired posteriorly-expanding median lamina, in 

 addition to its paired laminae, Avith which it forms a continuous series; this lamina 

 is itself sometimes marked off by a transverse sulcus from the median area of the 

 tergum. This median lamina of the last tergum visible from the dorsal side, 

 overlaps the tergal element of the next succeeding segment ; the tergum of this 

 segment is fused with its sternal element to constitute a subannuliform sclerite, 

 near the centre of which lies a plate, the anal operculum, which is the tergal 

 element of the last segment. Thus ten tergal elements may be traced with 

 certainty in almost all genera, the last being the anal operculum and the first the 

 short tergal area that lies between the carapace and the first large tergal plate of 

 invariable occurrence, namely the seventh from the end on the dorsal side. 



