J. W. JTJDD ON THE SECONDAKY ROCKS OF SCOTLAND. 



729 



and character even within exceedingly short distances. The strata 

 represented may he exhibited in a tabular form as follows, proceed- 

 ing from above downwards : — 



feet. 

 I. Sandstones and white marls, with numerous plant-remains and 

 occasional thin seams of coal. The Miocene basalts and volcanic 

 tuffs are seen to repose upon eroded surfaces of this set of beds. 

 This series is nowhere exposed in a section of more than 20 feet ; 

 but what its full thickness may have originally been, we have 

 no means of j udging 20 



II. Beds of white indurated Chalk with bands of flints. The Chalk 



itself is usually converted into an almost purely siliceous rock, the 

 various minute organisms in it, however, being still recognizable. 

 The fossils in these beds are all marine. Though no section 

 more than 10 feet in thickness of these beds can be anywhere 

 seen, yet it is evident that in places they must have attained a 

 very considerable development. Only here and there, however, 

 can they be traced, where some fortunate accident has exposed the 

 base of the great superincumbent masses of basaltic lava 10-f- 



III. Beds of white sandstone, without fossils, occasionally containing 

 many white quartz pebbles, and passing into conglomerate. 

 These beds have yielded no vestiges of marine life, but in places 

 contain much carbonaceous matter, and at one point a seam of 

 coal has been detected in their midst. Their thickness is very 

 variable, averaging about 100 



IV. Glauconite sandstone (greensand). Often highly calcareous in its 



upper part and passing into limestone, but still containing the cha- 

 racteristic grains of glauconite. At other points it passes into an 

 areno-argillaceous rock of a dark green colour, very similar in 

 appearance to portions of the Hibernian Greensand. The fossils 

 in these beds are very numerous and entirely of marine forms ; 

 although individuals are so abundant, however, the number of 

 species is by no means very great. The thickness of this marine 

 series is very variable, the maximum may be taken at 60 



We thus see that the Upper-Cretaceons series in the Western 

 Highlands consist of four members, two marine and two estuarine. 

 The exact age of the marine strata can be fixed precisely by the 

 fossils which they contain, that of the estuarine beds can only be 

 inferred from their relations to the marine series. 



The lowest series of beds (IV.) unquestionably represents the Ce- 

 nomanian or Upper Greensand, and in its mineral characters greatly 

 resembles the equivalent strata in England and Ireland. The fossils 

 which it contains place this identification beyond doubt ; they in- 

 clude the following species : — 



Nautilus Deslongchampsianus, U Orb. 

 Exogyra conica, Sow. (very abundant). 



haliotoidea, Sow. 



, sp. 



Pecten asper, LamTc. 



Pecten orbicularis, Mant. (abundant). 



quinquecostatus, If Orb. 



Serpula, sp. 



, sp. 



Spongia paradoxa. 



Unfortunately no Ammonites have been detected in the Scottish 

 deposits ; and it seems probable that the Upper Greensand of this 

 northern area was deposited under more littoral conditions than the 



strata of the same age in England. 



The series II. contains BelemnitelJa mueronata, Schloth., with a 



