236 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 2, 



any resemblance to the present one is described by Baron de Ryckbolt 

 under the name of Chitonellus Barrandeanus ; but, so far as may be 

 judged from De Ryckholt's figure of the plate, the relationship does 

 not appear to be specific. 



The general form of this plate, its great elongation, and the 

 merging of the anterior into the lateral margins are features that 

 belong rather to Chitonellus than to Chiton proper. Not knowing, 

 however, anything of the form or development of the apophyses, or 

 rather of that portion of the plate which was imbedded in the 

 mantle, I have doubtfully retained the species in the genus Chiton. 



4. Chiton. Spec. nov. ? Pigs. 9 & 10. 



An intermediate plate, short, very transverse, obtusely angulated ; 

 anterior margin concave; apex pro- 

 jecting, but not acute; median line Figs. 9 & 10. — Intermediate 

 arched ; dorsal area obscure, lateral Plate of Chiton, sp. ? 



areas not large ; apophyses wide, semi- ^^^^^^ ^^ ^^^ ^.^^^^ 



lenticular ; suriace apparently worn ; 

 length i inch, breadth -^ inch. 



There is no mistaking the type of 

 Chiton to which the present plate 

 belongs. Its form is that of the inter- 

 mediate plates of many recent species 

 of the common t j^e. Had it occurred 

 in Permian strata, it would most un- 

 doubtedly have been referred to Chiton 

 Loftusianus,Xing, to the middle plates 

 of which it bears great resemblance. 

 It would, of course, be premature to 

 identify it with that species at pre- 9. Upper view. 10. Lateral view, 

 sent, upon the strength of a knowledge 



of a single plate ; and it would be just as premature to say positively 

 that they are distinct, upon the strength of their being found in dif- 

 ferent formations, particularly as several species of Mollusca are al- 

 ready known to be common to the faunae of both periods. 



Besides the preceding plates, there is a cast of a patelliform shell 

 among Mr. Burrow's specimens that may possibly be a plate of a 

 Chiton or Chitonellus, It is | inch long, rather convex, and slightly 

 flanged marginally ; and a posterior plate of an undoubted Chiton 

 rests upon one side of it. I do not describe it with the other plates, 

 because I cannot detect traces of apophyses, nor satisfy myself as to 

 its shell- structure, nor yet perceive anything conclusive of its rela- 

 tion to this family. 



These species appear to be the first Chitons that have been ob- 

 served in Carboniferous strata in England. In the equivalent rocks 

 of Belgium Chitons have been known to occur since 1843, when 

 Professor De Koninck described two species in his ' Description des 

 Animaux Fossiles du terrain Carbonifere de Belgique,' pp, 321-323. 



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