5t6 AN ARACHNID FROM THE COAL 



well preserved it appears as a narrow rounded thickening or 

 'bead.'* 



The segmentation of the abdomen is clearly and strongly 

 marked. There are eight obvious segments, in addition to 

 the rounded anal plates. Segments i to 7 are subequal in 

 length (antero-posteriorly), the second being slightly the 

 longest, and those behind it showing a certain gradation. 

 The hind borders of segments 2, 3, 4, and 5 are markedly 

 raised and thickened, especially towards the middle linej. 

 The hind borders of segments 6 and 7 are not thickened : 

 they are clear-cut and finely granulated, the granules, other- 

 wise scattered, being ranged along the sutures in an orderly 

 row. The most striking characteristic of the abdominal 

 plates in comparison with those of most Anthracomarti is, 

 however, the fact that in each of them the median portion 

 is straight transversely and the side-pieces (lateral laminee) 

 are also straight, though inclined obliquely backwards. So 

 that where these laminae are developed (segments 4 to 8) the 

 segments are sharply angulated, whereas in nearly all Anthraco- 

 marti they are curved, the laminae following out the line of the 

 median plate (see fig. 6, in which a typical Anthracomartid 

 is represented in outline). The lateral laminae are not marked 

 off by sutures or in any other way from the median portions of 

 the plates. This is one of the chief reasons for regarding the 

 plates as those of the ventral surface, for it appears to be very 

 generally the case in the Anthracomarti that whereas the 

 tergites and their laminae are separated by sutures, the 

 sternites and the corresponding ventral laminae are not so 

 separated, but form in each segment a single undivided 

 plate. 



* A somewhat similar beaded edge in Kreischeria, another genus of Anthraco- 

 marti, is regarded by Fritsch as a row of reduced plem-al plates such as form a 

 fringe round the abdomen in certain genera (e.g. in Anthracomartus). 



t The thickening of the hind borders of some of the segments is perhaps a 

 further difficulty in accepting the view that it is the internal surface of the plates 

 that is shown. Prominent hind-borders to some of the abdominal sternites are a 

 characteristic of many modern Opilionids, but I am unable at present to say 

 whether in their case these plates have also thickened edges internally. 



