REPORT ON THE POLYPLACOPHORA. 37 



Blainville 1 attributes the genus Oscabrelle to Lamarck, with Ghitonellus Icevis as its 

 type, and the genus Chitonelle to himself, with Chitonette larvceformis. 

 These facts may be tabulated thus : — 



1S15 Cryptoconchus porosus, n. sp., Blainv. (Burrow), genus and species retained. 



,, ,, larvceformis, n. sp., Blainv. (Burrow), species retained. 



1818 Cryptoplax larviformis, Blainv. (Blainville), genus retained. 



„ ,, depressus, n. sp. (Blainville), species unrecognised. 



1S19 Chitonellus Icevis, n. sp. (Lamarck), species most probably a synonym for Cryptoplax larvceformis. 



,, ,, strialus, n. sp. (Lamarck), species retained. 



1825 Oscabrelle Imvis, Lam. (Blainville). 



„ Chitonelle larvceformis, Blainv. (Blainville). 



183G Cliitonellus Ixvis, Lam., Chitonellus striatus, Lam., Chitonellus fasciatus, Quoy and Gaim., 



Cliitonellus oculatus, Quoy and Gaim. (Deshayes). 



From this it is clear that Cryptoplax takes precedence of Chitonellus and must be used 

 for pore-bearing species, Cryptoplax larvceformis, Blainv., being the type species. The 

 name Chitonellus may be retained for those species without pores if it should be deemed 

 advisable to maintain this distinction. 



I find that the late Dr P. P. Carpenter had arrived at a similar conclusion, as in his 

 MS. he states, " There being two names in use for the group, I have kept Lamarck's name 

 (the best known) for the non-porous and Blainville's for the pore-bearing species." 



Owing to the fact of pores having now been proved to occur in Chitonellus striatus 

 (see p. 40), all the species mentioned above must be relegated to the genus Cryptoplax, 

 with the doubtful exception of Chitonellus oculatus. 



The small size of the pores in this group and their tendency to disappear inclines me 

 to consider that their presence or absence taken alone is a totally insufficient character 

 upon which to found a generic distinction. 



There is no need to enter into a discussion of any later generic synonymy, as none of 

 the proposed names can stand. 



Genus Cryptoplax, Blainville. 



Cryptoplax larvceformis, Blainville (PL III. figs. 12a-12m). 



Cryptoconchus larvceformis, Blainville, Burrow's Elements of t Concliology, 1815, p. 191, pi. xxviii. 



figs. 2-4. 

 Cryptoplax larviformis, Blainville, Diet, des Sci. Nat., 1818, vol. xii. p. 124. 

 Chiton cliitonellus, Blainville, Diet, des Sci. Nat., 1825, vol. xxxvi. p. 550. 



„ %vermiformis, Blainville, Diet, des Sci. Nat., 1825, vol. xxxvi. p. 553. 

 Chitonelle larvceformis, Blainville, Manuel de Malacologie, 1825, p. 603, pi. lxxxvii. fig. 6. 

 Chiton fasciatus, Quoy and Gaimard, Voyage de l'Astrolabe, Zoo]., 1S34, vol. iii. p. 408, pi. Ixxiii. 



figs. 21-29. 

 Chitonellus fasciatus, Deshayes, Lamarck's Hist. Nat.'Anim. s. Vert., 1836 (ed. 2), vol. vii. p. 482. 



1 Manuel de Malacologie, 1825, p. 603. 



