CLASSIFICATION. 9 



" Cancellariidas," in this way providing his bow with two strings. Tate, in the 

 appendix to Woodward's ' Manual,' places it in the " Cancellaridaa ;" Stoliczka, in 

 the ' Palseontologia Indica,' places it with a query in the Trichotropidge ; whilst 

 Fischer actually places Purpurina amongst the Littorinidse. The latter author 

 assigns no reason for his conclusion, merely observing that Stoliczka's approxima- 

 tion of the genus to Trichotropis appears to him a very doubtful determination. 

 This subject has never been attentively studied by English palaeontologists, partly 

 owing to some of them having confounded Purpurina with Lycett's genus 

 Purpuroidea, and partly perhaps from the difficulty hitherto experienced in 

 obtaining good specimens from our English beds. 



The results are that an extremely well-marked group, judging, of course, from 

 the shell alone, has been regarded as having affinities with Purpura, with 

 Gancellaria, with Trichotropis, with Gerithium, with Littorina, and with Turbo. 

 In fact, in this short-lived genus Purpurina authors have noted features character- 

 istic at once of the Siphonostomata and of the Holostomata, of the Tectibranchiata 

 and of the Scutibranchiata, of the Toxoglossse, Rhachiglossse, Taenioglossse, and 

 Rhipidoglossae. 



From this very remarkable case we may draw the inference that probably it is 

 not easy to lay down the law as to family affinities in respect of Mesozoic fossils, 

 and for this reason we should deprecate the criticisms of certain zoological martinets, 

 who are only too ready to find fault with the palaeontologist. There is also a 

 second lesson to be learnt, viz. that in all probability there was a greater blending 

 of common elements in the Mollusca of the remoter past than there is at the 

 present time, and that consequently the rules of classification applicable to existing 

 creatures must not be too rigidly enforced. In fact we must use our system with 

 a view to the circumstances of the case and not allow it to tyrannise over us. 



But then comes the question, which must be faced by any one who has under- 

 taken to deal with the Jurassic Gasteropoda, where are we going to place 

 Purpurina in the forthcoming Memoir on the Gasteropoda of the Inferior Oolite, 

 seeing that it occupies such an important position in that series ? Although I 

 have my doubts about its being a true Siphonostome any more than Amberleya, yet 

 bearing in mind the idea of the original founder of the genus, and, moreover, 

 justified by the authority of Prof. Tate, I have concluded to place this genus at 

 the head of the list, though leaving the question of family in abeyance. 



Another still more important genus, eminently characteristic of the Inferior 

 Oolite, is Amberleya. The authors of the ' Great Oolite Mollusca/ when they placed 

 Amberleya nodosa under the Littorinida? and Amberleya (Turbo) capitanea amongst 

 the Turbinidse, gave unconscious expression to a doubt, never yet cleared up, as to 

 which of these two great families the new Jurassic genus should be referred. 

 Subsequently both Deslongchamps and Lycett had no doubt that Amberleya 

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