BEITISH PALEOZOIC ASTEEOZOA. 



INTRODUCTION. 



PRELIMINARY STATEMENT. 



This Monograph deals with the structure and affinities of tliose Palgeozoic 

 fossils which are nearly related to the Asteroidea (Starfishes) and Ophiuroidea 

 (Sand-stars and Brittle-stars) of the present day. In order that it may be of 

 interest alike to the specialist and to the student 1 am prefacing the detailed 

 descriptions of genera and species by a somewhat long introductory section of 

 a more general nature. I hope that this section will render the later detailed 

 studies more intelligible, and help the reader to follow with greater interest the 

 bearing of the work upon theories of evolution and consequent hj^potheses. The 

 endeavour made to cover the dry bones of these forms with flesh is attended with 

 difficulties, but even if complete success is not attained, the effort may give a 

 clearer picture of the ebb and flow of life in the dim past and provide tangible 

 hypotheses for test by future research. 



I shall endeavour to show 



(1) That we can trace among the Palasozoic Asterozoa very near relations of 

 an ancestral stock from which the tw^o divergent branches of the true Asteroidea 

 and Ophiuroidea arose. 



(2) That from this "root-stock" branch-stocks arose. The forms belonging 

 to these branch-stocks are neither true Asteroidea nor true Ophiuroidea, but are 

 characterised by modifications peculiar to themselves. Certain of the branch- 

 stocks were dominant in their day, but have since become completely extinct. 



In fact, just as the most direct lineal ancestors of the flowering plants are 

 found to have been of relatively little importance in Carboniferous times, being 

 overshadowed by extinct tree-like Horse-tails and Club-mosses, so in the older 

 Palaeozoic rocks we obtain dominant forms of the Asterozoa which show 

 specialisation along lines not observed in recent groups. Scott's ^ statement Avitli 



' D. H. Scott, ' The Evolution of Plants,' Home University Library, London, 1911. 



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