President's Address. 3 



When a shale bed overlies a sandy one, the cast brought up 

 from the underlying layer by the burrowing worm is still a 

 cylinder of hardened sand, and not the flattened plant- like 

 impression produced by the cast formed out of the softer ooze 

 of the shale bed itself. To the foregoing group succeeds a 

 massive bed of calcareous grit or quartzite upwards of 30 feet 

 thick, pierced by vertical worm pipes, and also containing, 

 along certain bedding planes, the remains of small tubicolar 

 annelides (Serpulites Maccullocliii). Specimens of Orthocera- 

 tites have also been obtained from this bed — one by a brother 

 of Mr Clark of Eribol, and another by Professor Lapworth. 



The Silurian strata just described are overlain by a vast 

 mass of limestone divisible into several well-marked zones, 

 lithologically distinct. One feature, however, is common to 

 the whole series — that nearly every bed is more or less tra- 

 versed by worm casts ; indeed, some of the bands consist 

 almost wholly of these casts with a matrix just sufficient to 

 hold them together. The rough exterior so characteristic of 

 some of the limestones is partly due to this cause and partly 

 to the fact that the matrix has crystallised in a different 

 manner from the casts, which makes it more easily eroded by 

 denuding agencies. The lowest beds of limestone are sandy 

 and shaly, and contain two zones of serpulites, the highest 

 being about 30 feet from the base. In the overlying 300 feet 

 of limestone no fossils have yet been obtained in the Durness 

 area, but the late Mr C. W. Peach found an Orthoceras at 

 Inchnadamff which must have come from this horizon. 

 Higher up in the series there are several fossiliferous zones 

 yielding an abundant suite of fossils, comprising Maclurea, 

 Ophileta, Mttrchisonia, PUurotomaria, Orthoceratites, Lamelli- 

 branchs, Brachiopods, and Trilobites — an assemblage of fossils 

 identical with that obtained by the Geological Survey of 

 Canada from the lowest Silurian and uppermost Cambrian 

 strata of Canada and the eastern part of the United States. 

 Indeed, many of the forms are common to the two areas. In 

 the N'orth-west Highlands we do not find any beds succeed- 

 ing in natural order to the limestone ; in fact, there is now 

 only a remnant of what originally was a more extensive and 

 in all likelihood a much thicker formation. The highest 



