8 



to the edges of channels which are either now traversed by tidal 

 currents like the trough of the Thames, or appear, like the dry- 

 combes, to have communicated with the sea at some remote period. 

 From the above facts, Mr. Trimmer infers that the pipes in the 

 chalk of the part of Kent examined were formed by the action of the 

 sea on a low shore ; that they mark the boundaries of the ante-eocene 

 sea, and that they were subsequently submerged and covered by the 

 London clay. 



" On some remarkable Concretions in the Tertiary beds of the 

 Isle of Man." By H. E. Strickland, M.A., F.G.S. 



The north extremity of the Isle of Man consists of an arenaceous 

 pleistocene deposit, occujDying an area of about eight miles by six, 

 Ijounded on the west, north and east by the sea, and on the south 

 by the mountains of Cambrian slate which occupy the greater por- 

 tion of the island. The arenaceous formation attains in some parts 

 a height of about 200 feet above the sea, though the undulations of 

 its surface prove that considerable portions of the deposit have been 

 removed by denvidation. This district, comprising about fifty square 

 miles, furnishes perhaps the most extensive example in the British 

 Isles of a marine newer pliocene or pleistocene deposit. In the Isle 

 of Man the sea-clifFs on each side of this tertiary district afford a 

 good insight into its structure and composition. On the north of 

 Ramsey the cliffs average about 100 feet in height, and consist prin- 

 cipally of irregularly stratified yellowish sand, sometimes clayey, with 

 interspersed bands of gravel and scattered pebbles. The gravel is 

 chiefly composed of slate-rock, quartz, old red sandstone, granites, 

 porphyries and chalk flints, all of which occur in situ in the island 

 except the two last, which may have been drifted, the former from 

 Scotland., and the latter from the north of Ireland. About four miles 

 north of Ramsey the cliffs attain 150 feet. Here the lowest portion, 

 only visible at intervals, is a brownish clay loam, and the remainder 

 of the cliff is sand and coarse gravel, less distinctly stratified than is 

 the case near Ramsey, and containing rudely rounded boulders, some 

 of which are upwards of a ton in weight. They consist of granite, 

 and occasionally of carboniferous limestone. 



Organic remains are sparingly diffused in this deposit : Mr. Strick- 

 land enumerates twenty species. Of these five, viz. Crassina mul- 

 ticostata, Natica clausa, Nassa monensis, Nassa pliocena, and Fusus 

 Forhesi are not known in the British seas. Crassina multicostata 

 and Natica clausa are found living in the Arctic ocean, but the two 

 species of Nassa and the Fusus are unknown in a recent state*. 



* Mr. Strickland gives the following characters of three species of shells 

 found in the newer pliocene beds of the Isle of Man ; specimens of which 

 have been examined by several eminent conchologists in London, who all 

 concm" in believing them to belong to extinct species. 



" 1. Nassa monensis, Forbes, in Mem. Wern. Soc, vol. viii. p. 62. Small; 

 volutions about six, rounded ; suture deep ; ribs, nine on the first volution, 

 sti-aight, rather distant, strong, subacute, and slightly oblique. The fii-st 

 volution has thirteen, and the second six, distinct, regular, thread-like, spiral 



