22i 
THE GEOLOGIST. 
12. Chiton loftusiamis, King. Humbletou Hill. 
Caeboniferotjs. 
13. Chiton concent rimis, De Kon. "Vise. 
f gemmatus, De Kon. Yise. 
, var. Mosensis, De Ryckh. Vise. 
Erom 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 
only in the cretaceous and Jurassic formations that no traces have been discovered. 
Without doubt, this gap will be soon filled u]) ; 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 corclatiis, Chitonellas Hancockiamis, and Chitonellus 
distortus. He also revised the descriptions previously given of Chiton Loftusi- 
anns, King, and Chiton Howseanus, Kirkby; also of Chito?iellus antiquuSy 
Howse. 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 
that some of the plates of these fossil Chitons have at first sight to Patellce 
and Calyptriea., and recommends that special care should, therefore, always be 
taken in the determination of patelliform fossils. 
* See Quart. Journ. Geol. See, vol. xv., p. 607, and plate 16. 
