214 ACANTHOPLEURA. 



* Zona spinosa. Chiton yuwsua Sow., Gen. f. 1. 



\=Acantkopleura spinosa Brug.] 

 * * Zona spinulosa. Ch. tarmvokaefa Gray, Spicil. 



[==Plaxiphora.] 

 * * * Zona granulosa. Ch. asellus Lowe, Zool. Journ. 



[=Lep\doplewru*i p. 13.] 

 * * * * Zona rugoso-granulosa. Ch. asselloides Lowe. [= 



Trachydermon albus L., p. 70.] 

 ***** Z ona crinita. Ch. crinitus Wood, Index. \=Acan- 



thochites.~] 

 ****** Zona villosa. Ch. peruvianus Frembly. \=Chfn- 



jileura, p. 28.] 



******* Zona farinosa. Ch. cinereus Lowe. \==Traehyder- 

 mon, p. 68.] 



As neither of these sections were selected by Guilding as the typical 

 group, we are obliged to select a type for ourselves ; and of course 

 the choice must be limited to the species actually enumerated by name 

 in Guild ing's *cheme of sections. We must first exclude such species 

 as are already provided with generic names ; and glancing down the 

 list we therefore, eliminate section * * *, which falls into Risso's 

 earlier genus Lepidopleurus, and section *****, which belongs to 

 Acanthochites Risso. Of the five sections remaining, * * was 

 separated by Gray in 1847 under the name Plaxiphora. Section 

 ****** was denominated Chcetopleura by Shuttleworth in 1853 ; 

 and for the species included in sections * * * * and * * * * * * *, 

 Carpenter established the genus Trachydermon, in 1863. These 

 successive dismemberments have left only ihefirtft tectitm of Guild- 

 ing's arrangement, to represent the original genus ; and Chiton 

 spinoms, therefore, becomes the type of Acanthopleura Guilding. 



Unfortunately for science, few authors have arrived at this 

 result; but the fact that it rests upon principles "t nomenclature 

 from which there is no appeal, will, it is believed, be evident to all. 



Since Guilding's publication of the name, it has been considered 

 by the following systematists : 



1840. SWAINSON defines the genus (which he calls " Canth}>]< 

 <Miild."), and names "(7. spinom*, Sow. Gen., f. 1" as the 

 representative or type. No other species is mentioned. 



1847. GRAY defines the genus, including in it sections as follow.* : 



* A.periiri'in'i I, in., bicolor Ad., hennnli (Jray, <"//-"/m Sowb. 

 [==Chatopkurci -f- 



