MALCOLMSON OLD RED SANDSTONE. 343 



Red Sandstone. Jaws and teeth resembling those of the species of 

 Megalichthys and Holoptychus of the Bnrdiehonse strata occur both 

 at Elgin and on the Findhom ; but when it is considered that so 

 many singular and unknown forms have been already obtained from 

 these rocks, I do not think that I need conceal my impression, that, 

 in the present state of the inquiry, great caution is requisite in refer- 

 ring to particular genera fragments which may belong to creatures 

 having little analogy to any known forms. 



In a new species and genus of ichthyodorulite (figs. 1, 2, and 3, 

 drawing 30) belonging to the family of Ostraciontes, from Scat-craig*, 

 M. Agassiz observed that the arrangement of the cells and fibres of 

 which it is composed resembled that in the spines from the Ludlow 

 rocks ; and a small specimen from the Findhom is very similar in 

 form to one of those interesting fossils. Other specimens have a 

 structure like that of some singular bones and epidermal coverings 

 found in the mountain-limestone near Edinburgh, and presented to 

 the Museum of the Royal Society of that city by Lord Greenock ; 

 and in a polished section of the remarkable ichthyolite from the 

 Clackmannan coal-field, in Dr. Fleming's possession, I detected a bone, 

 the structure and outline of which correspond exactly with one 

 from the Findhorn (fig. 6, di^awing 20). This similarity of struc- 

 ture is, however, consistent with the widest difference in the exter- 

 nal form of the animals. 



Section through the Middle and Inferior Sandstones on the Burn 

 of Lethen (Section, PI. XI. fig. 4), showing the superposition of the 

 Cornstone Series to the Fish-beds of Lethen. 



[This section is described from Dr. Malcolmson's MS., with some slight verbal 

 differences, in Mr. Grordon's Memoir, pp. 33-36. In reference to the bitumi- 

 nized remains of fish, op. cit. p. 35, Dr. M. has added this note — " Many of the 

 Orkney and Cromarty fish are converted into bitumen ; and this seems most fre- 

 quently the case when they occur along with plants. In a nodule in Mr. Miller's 

 collection a cavity is filled with fluid bitumen." At the same page the following 

 is a corrected paragraph — " A fact of much greater importance is that of their 

 appearing to belong to the same plants recently discovered by Mr. Austen in the 

 Old Eed Sandstones of Devonshire, for an opportunity of examining the figures 

 of which I am indebted to the kindness of Mr. Lonsdale." And the following 

 note is added — " I have since found the same plants to occur abundantly in the 

 Orkney Islands and in Caithness. — March 21, 1840." 



The nodules mentioned, op. cit. p. 36, are also said by the author to " have a 

 semicry stall in e structure, radiated towards the surface; and the central parts 

 occasionally approach in appearance to septaria. They burn into a tolerable 

 lime. Their colour is pale-blue when first extracted, but they acquire a reddish 

 tinge on exposure, and when rubbed or struck ; and the animal matter of the 

 fossils has often left deep-red stains, from its action on the iron of the stone. 

 In minute stains of this kind in a nodule from Tynat, Mr. Gordon discovered 

 some very small fish, probably the young of Cheiracanthus. Many of the scales 

 and bones have the fine plum-blue colour of the Caithness fossils. One nodule 

 sometimes contains more than a single specimen." Dr. Malcomson also ob- 

 serves — '• It is not improbable that a fossil lately found at Duryden, in Fifeshire, 

 and figured by Dr. Anderson, in his ' Account of the Greology of Fife,' as a beetle. 



* Tliis fossil is also found in the sandstones of the Findhorn. It has no 

 central cavitv. 



