XX11 POLYPLACOPHORA. 



stand what his family groups really mean. 



In Nouv. Archives du Museum (2) iv, 1881, Rochebrune presents 

 the following arrangement : 



Family ACANTHOCHIT^ Rochebr., genus Acanthochites Risso. 



Family CH^ETOPLEUR^E Rochebr., genus Chcetopleura Shutt., spe- 

 cies cjigas Chem. ; and genus Acanthopleura Guild. 



Family CHITONIDJE Gray, genus Tonicia Gray, Lepidopleurus 

 " Risso " [ Ischnochiton], and genus Gymnoplax Gray [=Chiton 

 s. str.~\. 



In the Zool. Cap Horn, 1889, the following scheme is given : 



Family PROCHITONID^E, genus Schizoehiton Gray. 



Family LOPHYOCHITONID^E, genus Acanthochiton Leach. 



Family CH^ETOCHITONID^:, genus Acanthopleura Guild. ; genus 

 Chcetopleura Shutt. [ Plaxiphora -f- Chaetopleura]. 



Family CHITONIJD^;, genus Tonicia Gray ; genus Lepidopleurus 

 " Carpenter, 1879 " [=Ischnochiton -f Trachydermon -f Callochi- 

 ton !] ; genus Chiton L. [Ischnochiton + Chiton s. sir.]. 



It will be seen that the ideas of Rochebrune are so opposed to 

 those of the Carpenter and the writer that any criticism of them 

 would be useless. The same Parisian author has published many 

 diagnoses of Chitons believed to be new ; but owing to his failure 

 to mention the characters really diagnostic of genera and species, 

 but little use can be made of his writings. The majority of these 

 forms are still unfigured ; and of his figured forms it must be said 

 that Rochebrune has been signally unfortunate in his artists. Of 

 all the figures of Chitons published by him I have not yet seen a 

 correct one ; most are so radically bad that no dependence whatever 

 can be placed upon them. The same is true of his figures of fossil 

 Chitons. 



From the above sketch it will be seen that the chief workers upon 

 the classification of Chitons have been few in number, the publica- 

 tions of BLAINVILLE, GRAY and CARPENTER successively mark- 

 ing epochs in the taxonomic history of the group. 



