XXII POLYPLACOPHORA. 



stand what hi* family groups really mean. 



In (2) iv, 1881, Rochebrune presents 



the following arranp-ment: 



Family ATAN m<>< HIT.E Rochebr., genus Acanthochites Risso. 



1 'an illy ( '11 i; i Rochebr., genus Chcetopleura Shutt, spe- 



<gas Cheni. ; and genus Acanthopleura Guild. 



Family ('IHTONID.K Gray, genus Tonicia Gray, Lepidopleurus 

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

 .]. 



In the /,!. ( './/, I/nrn, 1889, the following scheme is given : 



Family PIUM-HITONID^E, genus Schizochiton Gray. 



Family LOPHYOCHITONID;E. genus Acanthochiton Leach. 



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

 Chcetopleura Shutt. [ Plaxiphora -f- Chaetopleura]. 



Family ( in i MII:, genus Tonicia Gray; genus Lepidopleurus 

 rpenter, 1879 " [ Ischuochiton + Trachydermon -f- Callochi- 

 ton !] ; genus Chiton L. [=Ischnochiton -f Chiton s. 8tr.~\. 



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, 

 luit 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 IIochebruDe 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 !>< 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. 



