5lS AN ARACHNID FROM THE COAL 



selves) to be nearly related to the Anthracomarti. They state 

 definitely* that " the abdomen in Cyphophthalmi consists of 

 nine complete segments besides operculum anale .... 

 We consider operculum anale in all Opiliones as a terminal 

 segment of which only the dorsal part is developed." The 

 likeness in respect of these features between the Cyphoph- 

 thalmi (Sironidse) and the Anthracomarti was pointed out in 

 1890 by Haase|. The homologies of the anal plates are not 

 discussed by Fritsch, who remarks that these plates presumably 

 represent two segments, but that their origin is so complex and 

 doubtful that the investigator can interpret them pretty much 

 according to his fancy|. 



The difficulties that arise in the attempt to homologize the 

 anal plates of the Crawcrook arachnid will be understood 

 from fig. 9, where this region of the fossil is shown diagram- 

 matically with the plates marked in accordance with Pocock's 

 conclusions, for comparison with fig. xob. It will be seen that 

 there is a general correspondence in the arrangement of the 

 parts, but that the anal plates are situated relatively further 

 forwards ; and in consequence the outer plate, the supposed 

 ninth segment, apparently obliterates the median portion of 

 segment 8. If this be really the inner surface of the integu- 

 ment it is of course possible that the external, the true ventral, 

 surface might show a different arrangement ; that there might, 

 for example, be on the outside some trace of a median piece 

 connecting the two lateral laminae which are all that is here 

 seen of the eighth sternite. But in any case it is plain that 

 this sternite cannot here, as in most other Anthracomarti, be 

 as complete as those that precede it (cp. fig. 10b). The outer 

 boundary of the supposed ninth segment is perfectly clear on 

 the right side; on the left and behind it is much less definite. 

 The anal valve itself has as usual a double border. Its inner 

 margin is very sharply marked, which could hardly be the 



* H. J. Hansen and W. Scirensen. On two Orders of Araclmida, pp. 9-10, 

 Cambridge, 1904. 



t E. Haase. Beitrage zur Kenntniss der fossilen Aracliniden. Zeitsch. d. deutscb. 

 geol. Ges., vol. 42, p. 629. 



} A. Fritsch, Palaeozoisohe Arachniden, p. 66. 



