404 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 1, 



In proof of the very local character of the coarse breccia, the 

 observer has only to move a few miles eastward to Reay, and, in de- 

 scending the banks of the little Bum of Isauld to the sea-shore, he 

 will find that there the fundamental granite has undergone no dis- 

 location, and that the conglomerate, or base of the Old Eed lying 

 on it, consists of pebbles which have evidently been rounded by the 

 long- continued action of waves upon a shore, while the lower part 

 of the flagstones, presenting the same predominance of sandstone as 

 above remarked, and containing some limestone, passes in even and 

 unbroken beds under the great mass of the Caithness series with 

 its fossil fishes. The order is represented in the section, fig. 12. 



Fossil Remains in the Caithness Flags. — I have little new matter 

 to add in respect of the animal remains of this deposit of flagstones. 

 The genera and species of the fishes are already well known ; but 

 I may state that a specimen of a Ooccosteus lately discovered by 

 Mr, Peach exhibits a vertebral column more completely ossified than 

 that of any hitherto -discovered specimen. Again, it is to be noted, 

 that the Aster olepis, found by Hugh Miller in the lowest beds of the 

 Orkney succession, has been detected, both by Mr. John Miller and 

 Mr. Peach, in the highest beds of Caithness. Of the prevalent 

 genera, Osteolepis, Dipterus, Cheir acanthus, Diplopterus and Ooccos- 

 teus, the fish usually lowest in the strata of Caithness is the Osteolepis ; 

 it may also be stated that a Pterichthys has lately been found in the 

 Orkney Islands. 



I must not omit to speak of the only shell, or rather shell-like 

 Crustacean, yet discovered in these flags, and which occurs abun- 

 dantly at Kirkwall in the Orkneys, and has also been found near 

 Lerwick in the Shetland Isles. This is a small Estheria, a Phyl- 

 lopodous bivalved Crustacean, such as are found in African and 

 South American rivers. It is about half-an-inch long, and marked 

 by sharp concentric lines of growth, and has the general aspect of a 

 small Astarte, or Venus. It occurs in certain localities in such 

 numbers as to form layers an inch or two thick, entirely made up 

 of the thin carapaces. It has been described for me by Mr. T. 

 Rupert Jones, and is named by him Estheria Murchisoniana. 



Description of a small Bivalve Orustacean from Caithness. 

 Estheria Murchisoniana, spec. nov. Woodcut, fig. 14, c,d (p. 408). 



The carapace-valves of a small bivalve crustacean, occurring plentifully on 

 some of the surface-planes of the Caithness Flagstones, near Wick, and also in 

 the Orkney and Shetland Isles, have been noticed by Hugh Miller and others *. 

 Their close resemblance to the shells of small bivalve molluscs formerly led to 

 their being taken for the shells of Venus, Cyclas, &c. ; but their supposed rela- 

 tion to molluscs having been doubted, some specimens from near Thurso, collected 

 by Mr. Peach, were given to me by Mr. Woodward ; and a far larger number, and 

 better preserved, from Kirkwall and Murkle Bay, were confided to me for exami- 

 nation by Sir R. Murchison last winter. 



In their substance, consistence, configuration, and size, these Httle valves offer 



* See Dr. Malcolmson's Memoir, antea, p. 351 ; Miller's ' Old Eed Sandstone,' 

 4th edit. p. 132, pi. 5. fig. 7 ; and Sir Eoderick Murchison's remarks above ; and 

 a*pp. 411, 413. 



