35 



NOTES OX THE BRITISH CHITONS. 

 By E. E. Sykes, F.Z.S., etc. 



Read November 10th, 1893. 

 PLATE III. 



This group has always afforded much difficulty to the student on 

 account of the external similarity of species which when disarticulated 

 are found to belong to different genera. I have therefore brought 

 together figures of the head, tail, and median valves of all the 

 British species so as to show the diverse characters of the insertion 

 plates. These figures are drawn from actual specimens, except in 

 the case of Hanleya Hanleyi, Bean. The classification is, in general, 

 that of Pilsbry,^ and may appear rather startling to those who are 

 in the habit of using the old genus Chiton for every mollusc with 

 eight valves. This old genus, however, like Turho and others, must 

 be split up in the light of our advancing knowledge. How strongly 

 habits cling may be seen from a very recent paper by an English 

 writer, who — speaking of other genera — states: " Sach fundamental 

 changes are the despair of naturalists, and if followed would necessitate 

 every collection in the kingdom being periodically pulled to pieces and 

 reorganised." This gentleman's view appears to be that conchology 

 was created for the benefit of his collection and not that his collection 

 should be a means of advancing our knowledge of the mollusca. 



Lepido2)leurus cancellatiis, Sow., 1839. PI. Ill, Fig. 3. 



Mr. Pilsbry suggests - that it may be identical with Chiton 

 Islandicus, Gmelin.^ I cannot accept this identification ; Gmelin's 

 description is very vague, and does not point more to this species 

 than to any other of the group. 



Lepidopleurus scahridiis, Jeffreys, 1880. PI. III. Figs. 4 and 7. This 

 recently described species appears to have been overlooked by Pilsbry; 

 it has not, so far as I know, been figured before. 



Lepidopleiirus onyx, Spengler, 1797. PI. III. Fig. 2. I believe 

 this to be the correct name of the species generally known as Chiton 

 asellus, Spengler ; it was considered by Jeffreys and others to be 

 C. einereus, L. I prefer, however, to follow Hanley,* and use the 

 name of C. citiereiis, L., for the species commonly called in Eugland 

 C. tnaryifiatus, Jeffreys, et and. lliirch^ has pointed out that C. 

 onyx was "a worn asellus.^'' What he overlooked, however, was that 



' Tryon's " Manual of Conchology," ser. i. vol. xiv. (1892-93), 



2 Ibul. p. 4. 



3 Syst. Nat. vi. p. 3206. 



* Ipsa Liunsei Conchylia, p. 17. 



5 Mai. Blatt, xvii. p. 113. 



