448 Bibliographical Notices. 



As in the first volume, the illustrations both of the species and 

 their structure are extremely good, though, unfortunately, the 

 details are not quite so sharp and clear in some of them ; the 

 antcnnoD (in some cases), instead of terminating in a fine thread-like 

 point, show a defined terminal button. The process by which 

 the figures are produced is probably largely answerable for this 

 trilling blemish. 



When completed the present work will, without doubt, be the 

 most satisfactory revision of the families and genera of the Lepido- 

 pfera Hcterocera which has ever appeared, either in our own or 

 any other language. Arxhuk G. Eutler. 



Manual of ConcJiologi/, Structural and Systematic. With Illustrations 

 of the Species. By George W. TRYoif, Jun. Continuation by 

 Henry A. Pilsbrt. — Vol. XIV. Polyplacophora {Chitons). 

 Philadelphia. 8vo. 1892-3. 



This most important and useful work on systematic conchology was 

 commenced in the year 1S79 by the late G. W. Tryon. That author 

 was responsible for the first nine volumes and part of the tenth and 

 the first four volumes of the second series, descriptive of terrestrial 

 moUusks. At his death in 1888 the work was continued by 

 Mr. Pilsbry, and from that time has been proceeded with without 

 interruption. 



The present volume is devoted to an account of four families of 

 Chitons, namely Lepidopleuridte, Ischnochitonidoe, Chitonida:^, and 

 !Mo])aliida3, the two remaining families, the Acanthochitida? and 

 Cryptoplacidte, being reserved for the succeeding volume. This 

 arrangement is to be regretted, as it will cause considerable incon- 

 venience to have an Appendix and the Index to the entire group 

 bound up in a separate volume. 



The account of the Polyplacophora before us is by far the most 

 important hitherto published, and, indeed, the only one which can 

 pretend to anything like com])lcteness. The introductory portion 

 (pp. i-xxxiv) is devoted to a definition of the class, the description 

 of the shell, the girdle, and the external features of the animal. 

 Irregularities of growth and the collection and preservation of Chitons 

 are also treated of, and the chapter concludes with an account of the 

 progress in the study of these mollusks, the diff'erent classifications 

 which have been proposed by lilainville, Guilding, Gray, H. and A. 

 Adams, Shuttleworth, ^liddendorff, P. P. Carpenter, Dall, and 

 Fischer, and the synopsis of the classification adopted by the 

 Author, with an analytical key to the genera. The classification 

 *' is based mainly upon characters furnished by the articulating 

 surfaces of the valves.'' In this connexion ^[r. l^lsbry writes: — 

 " The hard structure in this group is comparable to the vertebrate 

 skeleton in the great variety of stresses to which it is subject. 

 Each valve is not oidy acted upon by external forces and its body- 

 muscles, but by the valves before and behind it and by the girdle. 



