lEEDALE : THE CHITONS OF THE KERMADEO ISLANDS. 39 



The name chosen by Tliiele was Clathropleura, Tiberi, tlie type of 

 which is given as Ch. sicuhis. Gray. It might be noted that at one 

 time Ch. areiis, Reeve, was considered synonymous witli tliat species. 

 The sub-genus ' Clathropleura ' is well represented in Australasian 

 waters, and the dissection of many species shows that the anterior 

 insertion-plate is normally eight-slit ; this is very constant, any 

 variation obviously being due to iiitersplitting. It is assuredly of no 

 import that the external sculpture of the anterior valve is more or 

 less tlian eight-ribbed. For these I proi)Ose {infra) to use Rhyssoplax 

 generically, and would state that wiiether the species is heavily 

 sculptured like Ch. canal iculatics, Quoy & Gairaard, and Ch. vatc- 

 clusejisis, Hedley & Hull, or practically smooth, as Ch. translucem, 

 Hedley & Hull, the internal structure is exactly comparable. 



If Ch. pelli.'i-serpentifi, Quoy & Gaimard, be now examined, it will 

 be found to diifer in every detail. The shell is quite dilferently 

 sculptured ; the scales are more solid and of a different character and 

 more looselv placed on the girdle ; the insertion-plates are coarsely 

 pectinate, of quite unlike appearance, the sinus scarcely appreciably 

 denticulate, and the anterior insertion-plate is never eight-slit, twelvt; 

 slits probably being the normal number. 



The reference of Ch. pellis-serpentis, Quoy & Gairaard, to a distinct 

 genus is the only course consistent with accuracy. It cannot be 

 considered congeneric with the species of Rhyssoplax, and it cannot 

 be ranked as a sub-genus of Chiton, as it is too different in every way. 

 Pilsbry's comparison of this species with Acanthopleiira is much nearer 

 the truth, but the intervention of Sclerochiton disconnects it rather 

 widely from that genus. For this species alone Thiele introduced 

 Sypharochiton, and therefore in this place the generic names 

 Rhyssoplax and Sypharochiton will displace the familiar 'Chiton'. 



Genus Rhyssoplax, Thiele. 

 Rhyssoplax, Thiele, "Das Gebiss der Schnecken, vol. ii, p. 368, 1893. 



Type (by monotypy), Rhyssoplax janeirensis = Chiton affinis, Issel. 



In the Revision, Thiele admits the shells associated with, as regards 

 shell characters, Ch. olivaceus, Spengler, as constituting a sub-generic 

 group, and for these he uses Clathropleura. The group is well 

 defined, and I would recognize it as a distinct genus, and would have 

 used Thiele's name, but upon investigation this usage is found 

 impossible. Clathropleura was introduced by Tiberi in the Bull. 

 Soc. Malac. Ital., vol. iii, p. 136, 1877, as a sub-genus of Chiton. 

 No diagnosis is given, but three species are cited, Ch. Icevis, 

 Ch. corallinus, and Ch. stdcatufi. No authorities are given for these 

 specific names, and in Das Gebiss der Schnecken, vol.ii, p. 367, 1893, 

 Thiele used this name and selected Ch. sicuhis, Gray, as type. 



Upon reference to the British Museum (ISTat. Hist.) copy of the Bull. 

 Soc. Malac. Ital., 1877, a peculiar complication is seen to occur. 

 Tiberi's sub-genus, as above noted, contained three species. On p. 143 

 Ch. Icevis, Pennant, is noted, and on the same page Ch. corallinus 

 {Lepidopleurus), Risso, is discussed. Then, on p. 145, Ch. sulcatus 



