7 

440 PROFESSOR GEIKIE ON THE 
comes in between them. These interposed beds form the high grounds of 
Lethen Bar and Broadshaw, and are well exposed along the course of the 
Muckle or Lethen Burn. They were carefully observed by Dr MAtcotmson, 
who found them to consist of a thick loose conglomerate, passing up into a series 
of shaly sandstones, shales, and clays, containing calcareous ichthyolitic nodules 
and remains of plants. Lithologically and paleontologically, these strata pre- 
sent a great contrast to those of the neighbouring Findhorn. We recognise in their 
dark grey colour, their flaggy and shaly character, their enclosed nodules with the 
familiar fibrous crust, the same type of deposits as those of Dipple, Tynet, 
and Gamrie. The fossil evidence entirely bears out this identification. From 
Clune and Lethen Bar many fine specimens were originally obtained by Lady 
Gorpon CumminG and Dr Matcotmson. The following species have been noted :-— 
Pterichthys latus (Ag.); P. Milleri (Ag.); P. productus (Ag.); P. cornutus 
(Ag.); P. oblongus (Ag.); Coccosteus oblongus (Ag.); C. maximus (Ag.); 
Cheiracanthus microlepidotus (Ag.); Diplacanthus striatulus (Ag.); D. 
longispinus (Ag.); Chetrolepis Cummingie (Ag.); C. curtus (M‘Coy) ; Osteolepis 
major (Ag.); Diplopterus macrocephalus (Ag.) ; Glyptolepis leptopterus (Ag.) ; 
G. microlepidotus (Ag.). 
It will be observed that no Holoptychius, Bothriolepis, or other species found 
in the Findhorn section occurs in this list, while, on the other hand, not one of 
the above fossils is to be met with on the Findhorn. But the Findhorn strata 
extend westward into the lower reaches of the Muckle Burn, where with their 
northerly dip, they overlie the Lethen sandstones and nodule-bearing clays, as | 
Dr Matcotmson first pointed out. They have not entirely filled up the great 
bay in the Highland hills between Forres and Nairn, or at least have been 
considerably denuded there. Hence the mass of the lower or Caithness series, 
several hundred feet thick, which rises into the Lethen hills between Rait and 
the Findhorn. | 
Owing, however, to the long promontory of gneiss and schist, which runs | 
through the hill of Urchany to the granite of Newton of Park, near Auldearn, 
the lower division of the Old Red Sandstone is again reduced to narrow limits, 
or disappears altogether as the upper series sweeps westwards by Nairn. But 
it reappears immediately on the west side of that ridge, and continues to flank 
the hills by Cawdor and Kilravock, until it swells out in the Drummossie Muir 
to the dimensions already referred to. 
From these facts it will be seen that two distinct margins or coast-lines are 
presented to us by the Old Red Sandstone of the south side of the Moray Firth. 
There is first the coast-line of Lake Orcadie, marked by the unconformable 
junction of the older or Caithness flag division upon the uneven surface and 
sinuous border of the crystalline rocks of the Highlands. Next comes the edge 
of the upper division which winds to and fro with ‘little regard to the earlier 
