342 ACEPHALA PALLIOBRANCHIATA. 



necessary to examine fossil as well as recent forms, nor 

 can the comparatively few of the latter now surviving in 

 existing seas, convey any just idea of their systematic 

 relations, so many of the connecting links between them 

 being lost to life. A visit to the quarries at Dudley, or 

 an Irish limekiln, or an oolitic section on the Dorsetshire 

 coast, or a green sand ravine in the Isle of Wight, will 

 furnish more sectional types, and afford more information 

 about the Brachiopods, than an examination of the finest 

 collection of the living species. In each of the above 

 excursions a different set of forms would be collected, for 

 the Brachiopods of the older palaeozoic epoch differed ma- 

 terially from those of the newer, whilst differences as great 

 are seen between those of the older and new secondary 

 epochs. Many of the palaeozoic genera have altogether 

 disappeared when we rise among the secondary rocks, and 

 in the latter we find forms which closely remind us of 

 existing species, but which, though very near, are yet un- 

 questionably distinct. In formations of all epochs a few 

 generic types are common, and the Lingulce of the earliest 

 sedimentary formations, presenting traces of organic life, 

 strikingly remind us of the species of that curious group 

 living in exotic seas at the present day. 



