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INTRODUCTION. 
The present volume being the first attempt at a systematic treat¬ 
ment of the Palaeontology of the Elasmobranch fishes, it seems a 
fitting occasion for briefly reviewing the bearing of the newly- 
collected evidence upon the various results that have already been 
attained in the study of the existing members of this great sub¬ 
class. Notwithstanding its imperfections, Palaeontology must neces¬ 
sarily be employed as the test—if it be not adopted as the basis—- 
for all morphological and taxonomic speculations; and though the 
pages of the Catalogue may indicate extreme imperfection in our 
knowledge of the past history of most groups, there are still a few 
well-ascertained facts which may be already profitably discussed 
with reference to the conclusions of recent Zoology. 
It is therefore proposed:—firstly, to enumerate the principal 
stages by which the most modern schemes of classification of the 
group have been elaborated ; secondly, to summarize the known 
and available palaeontological resources ; thirdly, to recapitulate the 
more important palaeontological results; and lastly, to discuss these 
results in the light of modern theories of taxonomy. 
Taxonomic Deductions from the Study of Decent Elasmobranchs. 
Erom the time of Aristotle and Pliny, fishes with a cartilaginous 
skeleton have been more or less clearly distinguished from those 
possessed of well-formed bones; and when Willughby and Pay in¬ 
augurated the era of modern Ichthyology in 1686, they assigned to 
the “ Pisces Cartilagjnei ” the lampreys, sharks, rays, and stur¬ 
geons b In 1738, Artedi 2 confirmed this arrangement, elaborating 
details, and applying the name of Chondropterygii to an “ order ” 
comprising the existing types just mentioned ; and Linnaeus 3 after- 
1 J. Raius, F. Willughbeii de Historia Piscium (1686), p. 22, 
2 P. Artedi, Ichthvologia, pt. v. (1738), p. 89, 
3 C. Linnaeus, Svstema Kalurte. l2tb edit. 
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