MEASURES OF THE TYNE VALLEY 51I 



the wings of cockroaches are the least rare. Of this nature 

 are the only arthropod fossils hitherto known from the 

 Northumberland and Durham coal field ; a few fragments of 

 cockroach wings were found in some Upper Coal Measure 

 shales on the banks of the Wear near Sunderland, and are 

 now in the Hancock Museum, 



But rare as are insects, and the higher Crustacea too, in 

 the Coal Measures, they are common in comparison with 

 arachnids. Scarcely a dozen specimens altogether appear to 

 be on record for Britain. Some of the coal fields of Bohemia, 

 Germany, and the United States have, it is true, proved much 

 more productive in respect of fossil arachnids than our own, 

 and a remarkably interesting body of information is now 

 available concerning the arachnid fauna of the coal period, in 

 particular through the admirable studies of Prof. Fritsch. But 

 the fact remains that arachnids of any sort are among the 

 rarest of Coal Measure fossils, and that this is especially the 

 case in Britain ; whilst from the coal field of Northumberland 

 and Durham no fossils of this nature have ever been recorded 

 previously. 



The Crawcrook specimen belongs to a group which has 

 long* been known as the Anthracomarti (corresponding with 

 the Meridogastra, Thorell, of Fritsch's classificationf). As 

 weeded out by Fritsch this group constitutes a primitive sub- 

 order of the Opiliones or Phalangidea, the familiar long-legged 

 " harvest-spiders."! Fritsch {Joe. ctt) recognizes as belonging 



* Since 1882. See E. Karsch, Ueber ein neues Spinnenthier aus der schlesischen 

 Steinkohle und die Aracliniden der SteinkoUenformatiou iiberhaupt. Zeitsoh. d. 

 deutsch. geoL Ges., voL 34 (1882), p. 556. 



t A. Fritscli, Palaeozoische Araclmiden, pp. 31, 65, Prag, 1904. 



J This view of the relationship of the Anthracomarti is not shared by two of 

 the highest authorities upon the existing arachnids. Dr. H. J. Hansen and Dr. W. 

 Sorensen of Copenhagen. In their work " On two Orders of Ai-achnida " 

 (Cambridge, 1904) they discuss the Anthracomarti and conclude that the group 

 should be dropped altogether until more is known of the forms composing it. 

 At that time, however, they had not seen Fritsch's work on the Palasozoic Arachnida, 

 in which a wealth of previously unobserved detail is described. Prof. Fritsch himself 

 has no hesitation in associating the Anthracomarti (Meridogastra) with Opiliones ; 

 he even speaks of most of them as Trogulids. Further, there are two Carboniferous 

 genera, Nemastomoides and Dinopilio, which he considers, apparently with excellent 

 reason, as belonging to the Opiliones veri. 



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