28 8. V. Wood, jun. — American and British Surface- Geology. 



a position as to prove that it lived there. They appear to me to be 

 conspicuously shells of the earlier part of the major glaciation, and 

 they are absent from the Scotch ^ and all other English Glacial beds, 

 as well as from all beds of post- Glacial age. The Nucula has been 

 identified with more than one species living in the Pacific, apparently 

 from conchologists not being acquainted with the full-grown Crag 

 and Glacial shell ; but from this full-grown shell the Pacific speci- 

 mens differ widely.* 



The Tellina is called by Mr. Jeffreys a variety of the peculiarly 

 Glacial species lata (calcarea or proxima), which lives in Arctic 

 seas, and characterizes the beds of the North-west of England and 

 Scotland, and is found in East Anglian beds of Hessle age ; but, 

 unless he has met with it since I inquired of him a few years ago, 

 he does not pretend that the shell itself (i.e. the variety as he calls 

 it) exists in a living state. These two forms of Tellina (lata and 

 obliqua), whether we call them varieties or species, lived together in 

 all beds from those of the Ked Crag to that of Bridlington ; but, as 

 far as yet known, the form lata is the only survivor of the two from 

 the stage indicated by the Bridlington bed. Considering the great 

 difficulties which beset the elucidation of Glacial formations, and 

 how small is the assistance furnished by Palaoontological evidence 

 towards that elucidation, I am surprised that the facts concerning 

 this Nucula and this Tellina have not met with more attention than 

 they have hitherto done. 



In conclusion, I beg, although I have dissented from some of 

 his views, to tender Mr. Geikie my congratulations on the produc- 

 tion of his able book — a work that will doubtless much extend the 

 interest felt in the evidences of an age which, although the latest 

 of geological periods, is, from its association with the history of 

 Man in our latitudes, the most important of any. 



P.S. — The whole of this paper having been in type before the 

 November number of the Quarterly Journal of the Geological Society 

 (No. 132) was issued, I was in ignorance of the tenor of the paper 

 in that Journal by Mr. Mackintosh, on the sections around the 

 estuary of the Dee ; but having become acquainted several years 

 ago with sections in that neighbourhood, as well as with the limits 

 and distribution of the UiDper Boulder-clay and Middle sand, I had 

 then satisfied myself of, and suggested to geologists the identity of 



1 Except the derivative fragment found by Mr. Jamieson in the gravel near 

 Aberdeen, referred to in a previous note on p. 26. 



'■* Five living species of Nucula with divaricated markings like Cohboldice are 

 known. They are confined to the Pacific Ocean, and have been described under the 

 following names, viz. N. mirabilis (from Japan), N. divarieata (China Sea), N. in- 

 signis (Japan), N. castrensis (Sitka), and N. Lyalli (Vancouver). The first named 

 is about one-third of the size of the full-grown Cohboldice, while none of the others 

 exceed a ninth ; and their hinge-teeth are from 4 to 9 fewer. The divaricated marks 

 in all five extend to the margin of the shell, while Cohboldice has round this margin 

 a broad belt which is free from them. It is possible, though hardly probable, that 

 all the specimens yet obtained of these five species are those of young individuals 

 which might have grown into a mature shell like Cobholdim ; but until a specimen of 

 the kind can be produced, it is as reasonable to identify any of these Pacific species 

 with Cohboldice^ as with the divaricated Nucula from the Gault. 



