ON THE SHELL-BEARING DEPOSITS AT CLAVA, AND OTHER PLACES. 509 



Supplementary Note hy Mr. Robertson on the Different Parcels of Clay and 



their Contents. 



One thing to be borne in mind in examining several parcels of clay 

 from the same deposit is that the contents of any two will scarcely ever 

 be alike. 



For example, in my first list (a) there are several species of Mollusca 

 not in Mr. Eraser's Ust, viz. — 



Astarte sulcata. 

 Axinus flexuosus. 

 Lepton nitidum. 

 Tellina calcarea. 

 Fusus antiqvMS. 

 Trochus helicinus. 

 „ Groenlandicus. 



On the other hand, in Mr. Eraser's list there are eight species not in 

 my first list, viz. — 



Astarte compressa. 

 Cardium edule. 

 Leda pernula, var. mucilenta. 

 Nucula tenuis. 

 Tellina Balthica. 

 Buccinum undatum. 

 Pletirotoma Trevelyana. 

 Trophon clathratiis. 



Some of these, however, are in my second list (J) derived from clar 

 taken from varions parts of the section (see preceding table). 



State of Preservation. — Many of the delicate shells are whole; yet 

 there are fewer perfect shells, or with the valves together, in Clava than 

 we usually find in the post-Tertiary clays of the Firth of Clyde. 



The number of species, also, is notably poorer in the Clava deposit than 

 in those of the Firth of Clyde. For example, Bissoa striata and its variety^ 

 B. parva, are abundant all through the Clyde beds ; but, so far as I have*^ 

 seen, they are absent from Clava. 



Of course, we have to take into account that the post- Tertiary fauna 

 of the clays on the east coast differ in several respects from those on the 

 west coast. This holds good to some extent also with regard to the fauna 

 of the present seas. 



D. R. 



Note to Preceding List of Foraminifera. 



Note. — The Foraminifera as a class are of very wide distribution 

 both as to latitude and depth, some being found in all seas, and from 

 brackish pools to the deepest soundings. It is worthy of note 

 however, that some of the genera found at Clava, and a few other 

 Scottish clays, are more restricted in range, being not only ' essentially 

 shallow-water species,' but (as seems more remarkable) to be found 

 chiefly in 'temperate and sub- tropical seas.' The Botalia, for example, 

 * have not been found within the Arctic or Antarctic circles, but tho 



