Illl I .") 1 



val\-e>. a meaning also favored by the etymology ; but in I'. / 



\^\^ he places (iiiiiiiinfi/ii.!- under <"/,//,, a synonym. In 



anv ca>e, tin- name (//////;////'/./ cannot I" V<T heen 



diaL r M>sed except in the uvneral way <|iioted above, and no-pecics 

 lias ever hecn rxpivss ly deH-naled a< hrlnn^Ji,^ to it. The name 

 has been ii>'il by <iray only in the instances above mentioned and 

 \va-. MS \ve have seen, considered a synonym hy him in his later 

 writings; hut it should he noted that the invpre.Vihle Kochehrune, 

 still Uflefl <; : n,iintj t /i.r in a generic sense, in order presnmahly, to 

 disguise his species; an unnecessary precaution, for his diagnoses of 

 Chitons generally defy indeiktificatioD of either genus or species. 



In conclusion : it is obvious that the name Chiton must be retained 

 for a group typified by one of Linnets original species ; and since the 

 tubereulatus is the only one of the original li.-t which has been or 

 can be identified, that species becomes the type of the genus. No 

 other position on this question is reasonable or tenable. 



The most natural primary division of Chiton is into two groups; 

 one to include all American and some Old World species, in which 

 the mucro is anterior and the scales smooth, the other to include Old 

 World species having the mucro subcentral and the scales striated. 

 As this division is based upon characters not always easy to see, the 

 following division into sections is more convenient. 



Section CHITON (restricted.) 



Median valves having a single slit in each insertion-plate; sinus 

 generally denticulate ; scales closely imbricating. 



Section RADSIA Gray. 



Median valves having two or more slits in each insertion-plate. 

 Section SCLEROCHITON Cpr. 



Median valves having a single slit in each insertion-plate ; teeth 

 of tail-valve tending forward; sinus smooth; scales of girdle 

 separated. 



Section CHITON s. str. 



Artificial key to specie* of Chiton. 



A. LATERAL AREAS RADIALLY SCULPT i KI:I>. 



a. Central areas having longitudinal riblets. 



b. Sides and ridge of central areas both sculptured. 



