Mn BRODIE, ON LAND AND FRESHWATER SHELLS, &c. 139 



Wiltshire. In the former place a bed of brown clay fills up fissures in the lower green sand, 

 containing bones of mammalia and other animals. The shells accompanying them belong chiefly 

 to the genus Pupa. In the latter locality a thick bed of brown clay affords the bones and 

 teeth of elephants, with remains of the horse and deer, a jaw of a fox, and some others. The 

 only shells hitherto found associated with them belong to the genus Helix. Recent shells also 

 occur with bones of numerous quadrupeds in clay and gravel near Ilford, Essex, where several 

 of the shells appear to be identical with those above mentioned. (See Loudon's Magazine, Vol. ix. 

 p. 263, and Lyell, Vol. III. p. 140.) Recent marine shells have also been discovered by Sir P. Egerton 

 in a bed of gravel in Cheshire, which are described in the second Volume of the Geological Pro- 

 ceedings. From the occurrence then of the same facts in these distant localities, it may be 

 asked, whether any conclusions might be drawn with regard to the probable contemporaneous 

 origin of these respective deposits ; and what argument might be founded on the excellent 

 preservation of many recent land and freshwater shells associated with bones of some extinct 

 animals, in strata, evidently of diluvial origin. 



Since writing the above, I have observed that there are two distinct beds containing shells. 

 The uppermost, is the fine, white sandy stratum, containing Helix and Paludina in great abun- 

 dance, with other shells. While the lower one, is a hard white marl (resembling chalk), charged 

 with numerous Pupa, small Planorbes, some Clausilia, and a very few Seed-vessels of Chara. 

 Large and small fragments of wood abound. This distinction of the two shell beds is necessary 

 to be observed, because they do not contain shells common to both. No Pupa, Chara or wood 

 occur in the upper sandy layer ; indeed the general characters of each are very different ; one 

 being a fine sandy shelly bed ; the other, a hard white marl, and in this latter formation 

 the bones were found. These two beds however lie within a few inches of each other, so that 

 the distinction is chiefly necessary, with reference to the different Testacea and Mollusca which 

 they each contain. 



P. B. BRODIE. 



Emmanuel Colelge, 

 April 28, 1838. 



The following Notes to the above communication are added by Professor Sedgwick. 



In a paper by J. Okes, Esq., published in the first Volume of the Cambridge Transactions (p. 175), there is 

 a description of some fossil remains of a beaver dug up from the bed of the Old West Water about three miles 

 south of Chatteris : and in a subsequent communication he described numerous fossil bones found in beds of 

 gravel which extend from Barnwell Abbey to Jesus Common. All the specimens were subsequently deposited 

 in the Woodwardian Museum: and, with those derived from the Barnwell gravel, were some species of land 

 and fresh water shells (Helix hortensis, &c.) well preserved and in a few instances retaining traces of their 

 original colours. Mr Okes considered these shells to belong to the period when the bones and gravel were 

 deposited. But the conclusion admitted of some doubt, as the pits from which the bones were derived gave 

 no clear sections ; and it mas just possible that the shells might have fallen down among the bones (during the 

 progress of the excavations), from the superficial part of the gravel. 



■Similar phenomena fell under my own notice, a year or two afterwards, while workmen were em])loyed in 

 excavating the foundations of the new houses at the west end of Barnwell. But there was still a dilliculty ; 

 because the sections did not shew the exact position of the shells, so as to prove that they were strictly con- 

 temporaneous with the deposit of the bones. The ob.servations of Mr Brodie have settled this question, and 

 there can now be no doubt that the shells above mentioned were as old as the period of the gravel. 



