POLYPLACOPHORA. XV 



prior to 1758, the date of LINNAEUS' Tenth Edition, in which four 

 species were described. By the addition of the forms of northern 

 Europe, this number is increased to nine in the twelfth edition of 

 the Systema. From this time on, large numbers of Chitons found 

 their way into English and Continental collections, and were figured 

 in the works of Chemnitz and others. Linne classed the Chitons 

 with the Cirripeds and Pholads, before the bivalves ; and this sys- 

 tem persisted in conservative conchological works during the first 

 few decades of the present century. In 1797, SPENGLER, a Danish 

 naturalist, published a good monograph upon Chiton ; but little real 

 progress was made toward a right appreciation of the rank of the 

 group, and the establishment of a natural classification, until 

 BLAINVILLE in 1816 (Bull. Philom.) separated them from the 

 other mollusks as a Class, to which he gave the name Polyplaxiphora. 

 In 1825, Blainville published the article upon Chitons in the Dic- 

 tionaire des Sciences Naturelles. In this work an excellent descrip- 

 tion of the entire organization is given, the parts of the valves are 

 definitely named, and the characters upon which the divisions of 

 the genus must be based are stated. The extraordinary insight 

 and genius of the French malacologist are manifest throughout 

 the systematic and structural part of this paper ; but the descrip- 

 tions of species, being unaccompanied by illustrations, have been 

 less useful. QUOY & GAIMARD, in 1834, gave an excellent 

 account of the species collected daring the voyage of the 'Astrolabe' ; 

 following the general lines laid down byde Blainville. Since 1834, 

 no systematic work on Chitons of more than local interest, has been 

 published upon the continent of Europe. 



In England, considerable species-work upon Chitons was done 

 prior to 1829, but all upon strictly Linn sean lines. In the year 

 1829, Rev. LANSDOWN GUILDING, residing in St. Vincent, West 

 Indies, wrote a valuable paper, in which he recognized five genera : 

 Chiton, Acanthopleura, Phakellopleura, Chitonellus, Cryptoconchus ; 

 defining each in an acceptable manner. Shortly after this, the discov- 

 eries of Frembly, Cuming and others, threw a multitude of new 

 and handsome species into the hands of the London conchologists. 

 BRODERIP and SOWERBY described most of these novelities in the 

 P. Z. S., 1832-1834, and in the Mag. of Nat. Hist, 1840; and Sow- 

 erby illustrated them in the Conchological Illustrations, published a 

 little later. These authors knew nothing of internal characters, 

 confining their attention to the superficial features of the shell only. 



