EEPOET ON THE POLYPLACOPHOEA. 39 



Quoy and Gaimard (loc. cit. p. 409) state : " II est jDrobable que neuf spiracules accom- 

 pagnent les valves de cbaque cote" ; mais nous n'avons jamais pu en voir cinq." As they 

 were on their guard we must admit their statement as being beyond doubt ; of course 

 they figure only five. 



In one of the specimens collected by the Expedition, the anterior five pairs of tufts are 

 readily seen, as is also the sixth tuft on the right side, but that on the left side is not 

 visible, nor the seventh or eighth pairs. Their apparent absence may, however, be possibly 

 accounted for by the fact that the skin is much wrinkled in the places where they might 

 be expected to occur ; but this does not apply to the interspace between the last two 

 valves, which is quite smooth and yet exhibits no trace of a tuft. 



Deshayes (loc. cit. Lamarck, ed. 2, p. 482) says of Chiton fasciatus, Quoy and Gaim., 

 " Sur l'extremite anterieure on remarque de chaque cote cinq ocelles d'un brun assez 

 ionce. 



Reeve figures the pores, 1 but in the otherwise much better figure of the same species 

 (Chiton fasciatus) in the Conch. Icon., fig. 2b, they are omitted, as is also the case in 

 fig. 2a, and no mention is made of them in the text. The normal number of pores is 

 present in the British Museum specimens, hence Reeve's silence on this point can only be 

 attributed to carelessness. 



Gould refers his specimen to CJiiton fasciatus, Quoy and Gaim. He is probably 

 correct in his identification, but his account is imperfect and does not correspond with the 

 figures. He makes no mention of pores. 



The brothers Adams 2 define the genus Cryptoplax as having the " mantle spinulose, 

 encircled with a series of setigerous pores." They include Cryptoplax striatus and Crypto- 

 plax oculatus and others in the same genus, although pores have not heretofore been 

 shown to occur in the former. They give a fair figure of Cryptoplax fasciatus, with the 

 nine lateral pores and a supernumerary one in front. 



In most cases the silence of authors concerning the presence or absence of pores or 

 tufts is not to be taken as an argument for their absence, as they are always small and are 

 often scarcely, if at all, visible in old and rubbed, dry specimens. 



The only conclusion at which we can arrive at in this species is that normally nine 

 pairs of tufts are present, but that in some specimens more or fewer of the posterior pairs 

 may be absent. This further leads us to the supposition that they may be entirely absent, 

 although we have at the present time no direct evidence in support of the last alternative. 



Cryptoplax striatus (Lamarck) (PL I. fig. 9, PI. III. figs. 9a-9m). 



Chitonellus striatus, Lamarck, Hist. Nat. Anim. s. vert. (ed. 1), 1819, vol. vi. p. 317, and (ed. 

 Deshayes) 1836, vol. vii. p. 481. 

 „ „ Sowerby, Genera of Shells, 1820-1825, No. 12, pi. cxxxix. fig. 4. 



1 Conch. Syst., voL ii. pi. cxxxv. fig. 4. 2 Genera of Eeeent Mollusca. 



