224 



THE GEOLOGIST. 



12. Chiton Loftusiamis, King. Humbleton Hill. 



Carboniferous. 



13. Chiton concentricus, De Kon. Vise. 

 f gemmatus, De Kon, Tise. 



, ■, var. Mosensis, De Ryckk. Vise. 



14. <j =— , — Viseticola, — 



, — Legiacus, — 



— — , — Eburonicus, • — 



15. prisons, Minister. Tournay. 



16. Nervicanus, De Ryckh. Tourney. 



Turnacianus, 

 mempiscus, 



( Chitonnettus ) cordifer, De Kon. 



TJppes, Devonian. 



20. Chiton laevigatas, I'r. Ad. Roemer. Grand 



21. — 



Tournay. 



22. 



23. 



24. 



tumidus, De Kon. Grand. 



Middle Devonian. 

 ' corrugatus, G. P. Sandberger. Willmer. 

 cordiformis, G. Sandberger. 

 prisons, G. Sandb. non Munster. 

 ^Sandbergiamis, De Ryckk. 

 sagittalis, G. and E. Sandberger. "Willmar. 

 N. sp. Plymouth (Geol. Surv. of England). 



From an inspection of this list, notwithstanding their relatively small number 

 when compared with living species, the Chitons have their representatives nearly 

 throughout the series of sedimentary rocks ; and that up to the present it is 

 onlviu the cretaceous and jurassic formations that no traces have been discovered. 

 Without doubt, this gap will be soon filled up ; for it is not probable that 

 animals, of which the first appearance dates back, so to speak, to the epoch in 

 which life commenced, should have had their race extinct for two geological 

 periods, the duration of which was not less than that of most of the others which 

 preceded or followed them. 



This list demonstrates, moreover, that next to the tertiary formation the 

 carboniferous deposits seem to contain the greatest number of species ; and 

 that the intermediate beds furnish the least. Two new species next form the 

 subject of a notice from Professor De Koninck: one he dedicates to Mr. John 

 Gray, its discoverer ; and the other to Dr. Wright, of Cheltenham. 



In March, 1859, Mr. J. W. Kirkby, of Bishopwearmouth, described some 

 new species of Permian Chitonidse, in a paper read before the Geological Society 

 of London,* namely, Chiton cordatus, Chitonellus Hancockianus, and Ghitonellus 

 distortus. He also revised the descriptions previously given of Chiton Loftusi- 

 amis, King, and Chitoti Howseanus, Kirkby; also of Chitonellus antiqiais, 



Ilowse. sp. 



The specimens which supplied 



Mr. Kirkby with materials for these de- 



terminations were all from the magnesian limestone of the neighbourhood of 

 Sunderland, in Durham, and chiefly from Tunstall Hill. 



Mr. Kirkby alludes in his paper (Op. Cit., p. 611) to the great similarity 

 thai some of the plates of these fossil Chitons have at first sight to Patella 

 and f r / V . and recommends that special care should, therefore, always be 

 taken in the determination of patelliform fossils. 



* See Quart. Jonrn. Geol. Soc, vol. xy., p. 607, and plate 16. 



