ON THE SIIELL-BEAEING DEPOSITS AT CLAVA, AND OTHEE PLaCE.S. 487 



A careful examination of the included blocks showed the following 

 interesting results : 59 per cent, consist of micaceous gneiss, about 10 per 

 cent, of granite, about 12 per cent, of quartz-schist and mica-schist, &c., 

 or in all 81 per cent, of the older crystalline rocks, and only about 17 per 

 cent, of Old Red Sandstone. 



One small block of Jurassic grit was detected in the shelly clay which 

 was sent to Mr. Horace Woodward, of the Geological Survey of England, 

 now engaged in mapping the Secondary rocks in Scotland, who has 

 kindly furnished the Chairman of the Committee with the following note 

 on the specimen : — ' There are gritty beds at the base of the Lias, in the 

 Lower Oolites, and in the Middle Oolites of the Brora country that closely 

 resemble your specimens. The nearest approach to it is in specimens of 

 Lower Oolite from Skye and Raasay. This particular bed is part of the 

 basement beds of the Inferior Oolite at the base of the so-called " Great 

 Estuarine Series." Curiously enough, we get no exposure of these beds 

 in the Sutherland region — only the upper parts of the Lower Oolite (with 

 the Bi'ora coal). Hence my opinion is that your specimen most nearly 

 approaches in character to laeds of Inferior Oolite (basement portion).' 



Notwithstanding the strong resemblance of this block of Jurassic grit 

 to strata in Skye and Raasay, the Committee are of opinion that it has 

 been dei'ived from some area of Secondary rocks in the North-east 

 Highlands. The nearest point to Clava where Jurassic rocks occur in 

 situ is about 12 miles due north of the shelly clay, on the shore of the 

 Black Isle, at Ethie, near the Sutors of Cromarty. The occurrence of 

 this solitary block of Jurassic grit is of considerable importance, as will 

 be readily admitted when we summarise the evidence bearing on the 

 direction of the ice-flow in the neighbourhood of Inverness (see map 

 for relative positions of Clava and Ethie, p. 499). 



Shells are found throughout the whole of the blue clay or at least 

 from within 5 or 6 inches of the top to the bottom of the deposit. They 

 are most abundant at a depth of 2 or 3 feet from the top. Many of the 

 shells are quite whole at all depths, others are partially crushed, others 

 are in a tender or decaying condition. In the lowest part of the clay 

 the shells are of a darker colour, and many of them are so decayed that 

 they will scarcely bear handling. At all depths fragments of Mytilus 

 are rather numerous, but so decayed that a whole specimen cannot be 

 obtained. The prevalent shell is Littorina littorea. 



In the case of many of the shells the epidermis is in perfect preserva- 

 tion, and no indications of ice-markings or abrasion coiild be detected 

 on any of them. The absence of ice-markings on the shells is a remark- 

 able feature, which serves to distinguish the Clava shelly clay in one 

 particular from the shelly boulder clay of Caithness and Orkney. In 

 the latter many of the shells are striated like the stones in the deposit.' 



It is important to observe, however, that some of the bivalves, such 

 as Astarte, with both valves attached, showing no signs of abrasion and 

 otherwise complete, were found with both valves crushed together. 



During the examination of the 'main pit' on October 15, 1892, the 

 following observations were made regarding the position of some of the 

 shells : — 



Astarte, single valve at 6 feet depth, concave side up. 

 Natica, ,, ,, mouth up. 



Littorina (large), ,, ,, mouth down. 



Natica, ,, „ mouth down. 



Natica, at 7 feet dei:)tb, mouth down. 



