GASTROPODA. 



Fam. I CHITONIDil^: Guilding. 

 Gen. CHELODES Davidson & King. 



18G7 Cliiton Barrande Syst. Sil. de BoiiCmo vol. Ill p. 175. 

 1874 Ghelodes Davids. & K. Qu. Journ. Geol. Soc. p. 1C7. 



Valves oblong, generally longer than broad; no laminae of hnertiim nor siitural lamina!; 

 apical area, of th,e inside higldy developed. 



It was only with some hesitation thiit I placed these curious fossils, of whicli 

 there are at least two species, amongst the Gastropoda as a genus of the Chitonidiie. 

 Led astray by some superficial points of resemblance I at first mistook them for one 

 of the aberrant group of the Brachiopoda, the Trimerellidi.E, and accordingly sent the 

 material I then could dispose of to Mr Davidson, when he jointly with Prof. King 

 was working out a Monograph on that group. They described the only form which 

 was then known as Ghelodes Bergmani ^), stating that it was none of the Trimerellida^, 

 but that it rather should be considered as belonging »to a section of the Coelenterates, 

 represented by Calceola and Goniophyllum». The authors do not expressly say whether 

 it should be regarded as the polyparium itself or as the operculum, but it seems most 

 likely, that they have thought the last to be the case. There is, however, no coi'al in 

 the Silurian formation of Gotland that possibly could have been provided with an 

 operculum of so peculiar a shape. The form of the calyx at its aperture is generally 

 circular or polyedric, never assuming such an outline as Ghelodes shows. 



There is not the least doubt that these questionable fossils belong to the same 

 genus as those which Barrande in the third volume of his grand work »Systeme Si- 

 lurien de la Boheme p. 175, pi. 16 fig. 19 — 28 has figured and named Chiton Bohe- 

 micus. Besides this there are several other palaeozoic fossils of almost the same shape, 

 which have also been referred to the genus Chiton. Closely related to the Silurian ones 

 are some detached plates, which Kirkbv has described and figured with some hesitation 



') Qii. .Tnunial Geol. Soc. 187'1, p. Hu 



