21 



March 23, 1854. 



Colonel SABINE, R.A., Treas. and V.P., in the Chair. 

 The following paper was read : 



" Note on an indication of depth of Primaeval Seas, afforded by 

 the remains of colour in Fossil Testacea." By EDWARD 

 FORBES, F.R.S., Pres. G.S. &c. Received March 22, 1854. 



When engaged in the investigation of the bathy metrical distribu- 

 tion of existing mollusks, the author found that not only did the 

 colour of their shells cease to be strongly marked at considerable 

 depths, but also that well-defined patterns were, with very few and 

 slight exceptions, presented only by testacea inhabiting the littoral, 

 circumlittoral and median zones. In the Mediterranean only one in 

 eighteen of the shells taken from below 100 fathoms exhibited any 

 markings of colour, and even the few that did so, were questionable 

 inhabitants of those depths. Between 35 and 55 fathoms, the pro- 

 portion of marked to plain shells was rather less than one in three, 

 and between the sea-margin and 2 fathoms the striped or mottled 

 species exceeded one-half of the total number. 



In our own seas the author observes that testacea taken from below 

 100 fathoms, even when they were individuals of species vividly 

 striped or banded in shallower zones, are quite white or colourless. 

 Between 60 and 80 fathoms, striping and banding are rarely 

 presented by our shells, especially in the northern provinces ; 

 and from 50 fathoms shallow-wards, colours and patterns are well 

 marked. 



The relation of these arrangements of colour to the degrees of 

 light penetrating the different zones of depth, is a subject well worthy 

 of minute inquiry, and has not yet been investigated by natural phi- 

 losophers. 



VOL. VII. D 



