Vol. XI] 



BERRY— FOSSIL CHITONS 425 



2. A short diagnosis of the more important differential 

 characters based upon the shell alone, and rendered as concise 

 as possible consonant with a reasonably certain identification of 

 the species ; 



3. In the case of hitherto undescribed species, a full de- 

 scription ; 



4. A statement of the known geologic and geographic 



range ; 



5. A list of the specimens examined, with pertinent data; 



6. Figures of the shell, including both exterior (dorsal) and 

 interior (ventral) views of a head, a median, and a tail valve, 

 wherever the condition of the specimens available makes this 

 possible ; 



7. Special remarks. 



No figures of any of the fossil species have been prepared 

 from recent specimens, and the diagnoses likewise are drawn 

 as exclusively from fossil specimens as the material has per- 

 mitted. In several instances both figures and diagnosis could 

 have been decidedly improved and amplified by a more extended 

 use of recent specimens, but it has seemed best for the present 

 to avoid this wherever possible. Similarly it has been thought 

 best to mention only shell characters in the diagnoses, not be- 

 cause of any desire to place an exclusive systematic value upon 

 them, but because, as has been stated, they are the only ones 

 preserved by the fossils. 



New Taxonomic Terms Proposed 



The following taxonomic terms are published for the first 

 time in the present paper : 



Oligochiton lioplax, new genus and species 



Leptochiton clarki, new species 



Ischnochiton (Lepidozona) sanctcemonicce , new species 



Callistochitonincc, new subfamily 



Callisto chiton decoratus ferminicus, new subspecies 



Key to Genera 

 The following key to the genera mentioned in this paper, it 

 is hoped, will prove reasonably workable. It is in considerable 

 degree artificial, but a purely phylogenetic key based upon the 



