Geological Society. 50/ 



gation of its corpuscules. 3. The granulated structure of these cor- 

 puscules. 4. The coarse granulated structure of the compartments 

 of the radiating fibres. 5. The close parallel perpendicular arrange- 

 ment of the fibres of the crusta petrosa. 6. The irregular congeriCvS 

 of granules surrounding the fibres of the ivory. 7. The peculiar tor- 

 tuous appearance occasionally exhibited by these fibres. 



On the whole, Mr. Nasmyth observes, the several species of ani- 

 mals noticed in his paper seem to be nearly allied, and fitted to 

 exist under nearly similar conditions; and though the early eras to 

 which these Pachyderms must be referred, present, he says, consider- 

 able uniformity of circumstance, yet they must have demanded some 

 variety of detail in the animal organization. 



Finally, the characteristics in the minute structure of the tusks of 

 all the five animals betray, the author observes, greater varieties than 

 are found to exist even betwixt some genera possessed of tusks ; and 

 if it be established that specific differences positively do exist among 

 all these animals, then the value of this kind of observation is great; 

 but if the five animals are all to be grouped in one category, then this 

 mode of observation is of no value in palseontological researches. 



Nov. 16. — " 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, occupying an area of about eight miles by six, 

 bounded 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 denudation. 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 diffiised in this deposit : Mr. Strick- 

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

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

 Forbesi are not known in the British seas. Crassina multicostata 

 2L 2 



