2 BRACHIOPODA. 



lineage. The Lingula-hed. of the upper Cambrian system 

 is well known ; and other palaeozoic strata contain 

 equally rich mines of similar wealth. But although 

 the number and variety of recent Brachiopoda are not 

 equal to those of former days, the difference does not 

 appear to be so great as has been usually represented. 

 Mr. Davidson, who is perhaps the greatest authority on 

 the subject, says that there are 20 Silurian, 25 Devo- 

 nian, 19 Carboniferous, 12 Permian, 12 Triassic, 14 Ju- 

 rassic, 12 Cretaceous, 10 Tertiary, and 14 recent genera 

 and subgenera; so that we seem to have improved 

 in this respect on the middle ages, and future genera- 

 tions may exhibit a further advance, and even rival the 

 primeval era. The comparative rarity of Brachiopoda 

 in modern times may be easily accounted for. They 

 mostly inhabit rocky and stony parts of the sea-bed, 

 which cannot be reached by the dredge without great 

 risk of its being lost or injured, although they are gre- 

 garious and occur in vast numbers under favourable 

 circumstances. My late friend, Dr. Lukis, found more 

 than 200 specimens of Argiope cistellula on a single 

 stone brought up from a depth of 20 fathoms off Guern- 

 sey; and I have myself repeatedly taken Terebratula 

 caput -serpentis and Crania anomala in such profusion 

 on the western coasts of Scotland, as to be compelled 

 by a sheer embarras des richesses to throw many 

 hundreds overboard in the course of a day's dredging. 

 Even the comparatively rare T. cranium is no exception. 

 I have counted seventy specimens, although broken and 

 imperfect, which came up in a single haul off the Shet- 

 lands. Terebratella Spitzbergensis, which was at first 

 accounted extremely scarce, now appears, from Dr. Otto 

 TorelVs researches, to be by no means uncommon in its 

 native haunts ; and I lately picked up two or three fossil 



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