260 ON THE PERMIAN CHITONID^. 



nearer approach to the typical forms. The following species (C. 

 distortus) seems to be its nearest relation known, as its processes 

 of insertion, though specifically distinct, have a strong general 

 likeness. 



The only locality of C. HancocManus is Tunstall Hill, where it 

 occurs rarely in the shell-limestone. 



It is with great pleasure that I name this species after my 

 friend Mr. Albany Hancock, of Newcastle-on-Tyne, to whom I 

 have been long indebted for advice and assistance in my pal^on- 

 tological studies. 



3. C. DISTORTUS, spec. nov. PI. XIII., figs. 28, 29, 30. 



Intermediate plates irregular in form, transverse, angulated me- 

 dianly ; posterior margin angulate or subangulate, with an apex 

 more or less prominent ; anterior margin obtusely and re-enter- 

 ingly angulate; surface divided into two unequal areas by an 

 elevated median ridge or keel^ from which each area slopes some- 

 what steeply; surface smoth (?); anterior process of insertion 

 very large, being almost as long as the exposed portion of the 

 plate, the median keel is continued over its surface, and projects 

 beyond its extreme margin, on each side of the keel the process 

 is slightly sinuate, and on the one side (partially) it is denticu- 

 lated ; a reflexed process of triangular shape bounds the under 

 surface of the posterior margin. 



Together with the plates just described, I have figured another 

 that is also smooth, as one that probably belongs to the same 

 species. But, though there is a probabilty of this, there is also 

 a possibility of it representing one which is distinct. Like the 

 preceding plates, it is unsymmetrical and of irregular growth ; 

 these features, with its smooth surface, are the only characters 

 supporting its specific af&nity to C. distortus ; and, as it wants 

 the strong median keel, the angularity of outline, and the large 

 development of the anterior process of insertion which distinguish 

 the plates described, it is evident that its specific relation to them 

 is questionable, though at the same time there are scarcely 

 sufficient data upon which to found a new species. So that for 



