Notices of Memoirs — Mr. Pengelly's Essays. 77 



Northam Burrows. "The pebbles, or boulders, vary from balf an 

 inch to a yard in mean diameter, the majority being about nine 

 inches. The greater number of them are oblate spheroids, but 

 occasionally prolate and nondescript forms present themselves." 

 They are derived from the Carboniferous grit of the district, and 

 without doubt came from the cliffs westward of the ridge, — between 

 Northam Burrows and Hartland Point — the southern shore of the 

 bay. 



" Seaward from this ridge, the tidal strand at first consists of 

 small pebbles, of which the great majority are also of grit, whilst a 

 few are of flint. Beyond this, to the low-water-line, it is composed 

 of fine sand, beneath, and frequently projecting through which, are 

 large accumulations of tenacious blue clay and vegetable matter, 

 containing roots, trunks, and branches of trees. The vegetable 

 remains are known as 'The Submerged Forest of Barnstaple Bay.'" 

 The clay is in some places six feet thick, and reposes on a bed com- 

 posed of rounded and angular fragments of the grit of the district, 

 which, with the exception of the angular pieces only, resembles in 

 all respects the Pebble Eidge. 



The present position of this Forest-bed may be hypothetically 

 explained either by a subsidence of the country, or by the removal 

 of some natural breakwater which formerly protected the Forest 

 from the ravages of the sea. Mr. Pengelly shows that the former 

 supposition is the only one with which the facts agree. 



" That the entire country around Barnstaple Bay has undergone 

 upheaval in times geographically recent, is established, beyond a 

 question, by the fine Kaised Beaches which fringe its coasts." It is 

 obvious, then, that the Forest and the Eaised Beach represent two 

 distinct periods. Mr, Pengelly regards the Beach as the more 

 ancient — that the elevation preceded the depression, and that during 

 the Forest era the height of the Eaised Beach above the sea-level 

 was, at least, twice as great as it is at present. 



He finishes by remarking "how utterly fallacious must be any 

 conclusions based on the assumption that our country has stood still 

 ever since the ancient beaches were first raised." 



2. Until very recently but four specimens of fossil fish from the 

 Devonian rocks of Devon and Cornwall were on record, and two of 

 these were considered very doubtful. But now " the paucity is by 

 no means so marked as was then believed ; and this, not in conse- 

 quence of the discovery of new specimens, but because certain 

 fossils, formerly supposed to be sponges, have been found to be 

 veritable ichthy elites." Mr. Pengelly's object is to give an histori- 

 cal statement of the discovery and examination of the fossils 

 alluded to. 



In his own collection he has upwards of three hundred fragments 

 of Pteraspides from the Devonian rocks. " We have been taught 

 to believe that the Devonian System and the Old Eed Sandstone 

 System are of the same age, One of the greatest difficulties in the 

 way of the acceptance of this doctrine, was the fact that, whilst the 

 Old Eed Sandstones teemed with fossil fish, there were none in the 



