xv i POLYPLACOPHORA. 



The same is true i:, who in 1847, published a monograph 



lining 189 species in the Conchologia Iconica. The figures 

 of Sowerby and Reeve are generally good ; but they ignore inter- 

 nal characters, and tlu-ir 1< '.-mptimis are totally inadequate. J. E. 

 GRAY, in 1847, (Ann. Mag. Nat. Hist., July-August, and P. Z. S.), 

 proposed a system of classification of Chitonidce, embracing many 

 new genera, but largely based upon Blaiuville's article of 1825. 



s system is as follows : 



V, n-it limit >imj pores or tufts ofsjtiiic* <>n the sides. 

 A 9 7 'in 1 1 posterior valves divided 



'> several ' 'I of the cent ml -mli-e* into two lobes. 



a. Containing Chiton, Tonicia, Acanthopleura, Schizochiton. 



b. Containing Corcphium, Plaxiphora, Onithochiton, Enoplo- 

 clii- 



['-. Radsia, Callocliiton, Ischnochiton, Leptochiton, subsequently 



a-l.lrd by Gray.] 



B. The plate of insertion of all the valves with only a single notch on 

 The valves more or less covered ; the hinder valve 

 I [dales of insertion (as in the central valves'), with 

 only a single notch <i cat-h side, and a concave sinuosity below. 

 a. Contain.- M<palia. Katharina, Cryptochiton. 

 // Mi ' >/ >t ! i <i series of pores (each furnished with a tuft of spine*) 

 on each side. The plates of insertion of all the valves with only a sin- 

 gle notch on each tide which is sometime* rudimentary. 



a. Contains Cryptoconchus, Amicula, Acauthochites, Chiton- 

 ell 



Some inconsiderable transpositions and additions were made by 

 Gray in e, 1857. This classification is accepted by H. & 



A. Adams, in their Genera of Recent Mollutca, 1858; the two pri- 

 mary livi-i< dig being regarded as subfamilies ( Chitonince and Crypto- 

 plar, i. ni. The species of their lists in very many cases do 



not belong to the genera to which they are assigned, the lists having 

 been compiled without regard to the characters of the insertion 

 plates. The main defects of this system are the greatly exaggerated 

 importance given to the development of girdle-pores, and the imper- 

 fect apprehension of the features of the insertion plates. Some 

 yean before the date of Gray's last paper, J. R. Sm in i \\ORTH, 

 an Englishman by birth, Init nvidi-nt in Switzerland, studied the 

 Chitons carefully in the light of Gray's earlier paper, and published 

 i- of the group (Bern. Mittheil, 1853), making 

 a number of decided improvements in classification. 



