PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 279 



29,370. Sehastodes auriculatus (Girard) J. & G. San Martiu Island. 

 29,361. Sehastodes serriceps J. & G. San Martin Island. 

 29,374. Hetci'ostichus rostratus Grd. San Martin Island. 

 29,360. Murwna mordax Ayres. 

 Indiana UNiVEESiTy, November 15, 1881. 



OIV THE GENERA OF CHITONS. 

 BY \¥. H. DALL. 



PALEOZOIC FORMS. 



The long delay in preparing the illnstrations for the monograph of 

 the Ghitonidw by the late Dr. Philip P. Carpenter has been the occasion 

 of several calls from paleontologists for an abstract of the genera 

 adopted in his revision of the fossil species. In justice to Dr. Carpenter 

 it seems that the characteristics of the genera should be made i)ublic, 

 the material left by him on the Palaeozoic species being practically com- 

 plete and ready for printing. The JMesozoic and Tertiary chitons all 

 belong to groups represented by living species, hence the present ab- 

 stract relates solely to those of earlier date. The groups of recent 

 chitons, already reviewed by me in these Proceedings,* form the subject* 

 of the second more condensed abstract herewith. 



The first fossil chiton was fonn<l by Defrance in 1802, in the Eocene, 

 and described by Lamarck as Chiton <j rig none its is. If was only in 1834 

 that a second species, C. antiqnns Conrad, was obtained, on this occasion 

 from the Alabama Tertiary. 



The first palaeozoic chitons were found in the Carboniferous rocks of 

 Tournay, in 1830, but they were not described until 1839. Since then 

 numerous others have been brought together and described by various 

 authors, as well as a number of organic remains not belonging to the 

 CJnfonid(e which have wrongly been referred to the group. Dr. Car- 

 penter expended a large amount of time and moneys in examining 

 the typical specimens in American and European museums, making 

 several journeys for the purpose. His opinions, therefore, are entitled 

 to great weight. Some time before his death, at his request, we went 

 over the ground together, specimens and figures in hand, and the 

 opinion then formed that his work is worthy of great respect, and, so far 

 as facts are concerned, of entire confidence, has not been changed by 

 my subsequent studj' of his incomplete manuscrir)ts. 



An excellent digest of the history of fossil chitons to date of publica- 

 tion was given by De Koninck in 1857,t which was translated for the 

 Annals and Magazine of Natural History, of August, 1860, by W. H. 

 Baily. 



'*Vol. i, pp. 281-344, 1878. 



tBull. Acad. Roy. des Sciences de Belgique, 1857. 



