IREDALK : THE CHITONS OF THK KEKMADEC ISLANDS. 45 



Genus Lucii.ixA. 

 Zuctlma, Dall, Proc. U.S. Nat. r^fus., 1881, p. 290. 



Type (by raonotypy), Chiton co7i/ossus, Gould. 



Pilsbry for the Tonicioid Chitons accepted two genera lonicia and 

 Onithockiton, but separated these into two distinct sub-families, an 

 altogether artificial and obviously imperfect classification. Thiele has 

 so far amended the case that his conclusions read — 



Genus Tonicia, Gray. 



Sub-genus Lucilma, Dall. 

 Sub-genus Onithochiton, Gray. 



Section Onithoplax, Thiele. 



I have no hesitation in accepting the very close affinity of Tonicia, 

 Lucilina, and Onithocliiton, but 1 think that it is best expressed bv 

 accepting each as of generic rank. Tliere can be no doubt that Thiele's 

 action in associating these forms is an improvement on Pilsbry's, and 

 it has the additional advantage of being based on examination of the 

 radulae of tlie Chitons. As, however, OnHhocliiton is well differentiated 

 by means of its posterior valve lacking teeth, I consider the usage 

 of this as generic should be maintained. I include the genus Z«c?7«'wrt 

 to note that it lived at the Kermadecs, small valves being not 

 uncommonly met with in shallow water dredgings. One specimen 

 was obtained from a piece of coral pulled out of 6 feet of water at 

 low tide, but 1 refrain from describing it ; too many immature 

 specimens have been lately described, and I do not think that many 

 writers have studied the long series of juveniles that is necessary 

 to understand the great changes that take place between the juvenile 

 and adult in many species. 



Genus ONiTHOCHiToif, Gray. 

 Onithochitou, Gray, Proc. Zool. Soc, 1847, p. 65. 



Type (by subsequent designation, Gray, 1847), Chiton undulatns = 

 Onithockiton filholi, liochebrune. 



It seems worthy of record that at the place cited. Gray introduced 

 the genus Onithockiton with the diagnosis: "The hinder valve witli 

 a produced terminal apex ; plate of insertion entire, rounded ; valves 

 thick; mantle covered with spines, bristles, or chaff-like scales." 

 On p. 67 is noted : " This genus (Acantko/zleura) gradually passes 

 to Onitkochiton," and on p. 68 we liave given — 



'■ Onituocuiton. 



0. gaimardi . . Chiton ffaimardi, TMaiuv., 54^6. 



0. hirtosHs . . Chiton hirtosus, Plain v., 5-16. 



O. undulatus . . Ck. undiilatus, Van Diemen's Land." 



Later, typifying the genera of Mollusca, Gray (same Proceedings, 

 p. 169) wrote : — 



" Onythochiton, Gray, 1847 . . Ch. undulatus.'''' 



