Geological Society. 515 



— Astartc borealis, which occurs in a fossil state in the crag and living 

 in the Arctic seas, and Astarte propinqua, a new shell. Mr. Lands- 

 borough gives a list of the twenty-seven species collected by him, 

 nineteen of which are common in the adjoining seas, six are known 

 to exist in the Arctic seas, and two, Natica glaucinoides , a crag fossil, 

 and Astarte propinqua, are believed to be extinct. 



Post-Tertiary Deposits. — The author prefixes to his account of 

 these beds a notice of the older formations in that part of Ayrshii'e. 

 The prevailing rock is red sandstone, which, at almost every point 

 on the coast, has been worn, by the former action of the sea, into 

 cliffs, which indicate a change of level of about forty feet. The ter- 

 race at the base of the cliff, Mr. Landsborough states, may be con- 

 sidered a marine raised beach, and the shells contained in it are, with 

 two exceptions, one of which is doubtful, of existing species. 



At Ardrossan, a deposit twenty feet above the level of the sea, 

 and at Kelly, the soil which covers the base of the inland cliff to the 

 height of thirty feet, are full of common marine shells. Similar beds 

 are stated to occur in the islands of Arran, Cumbra, and Inch Mar- 

 nock. In the parish of Stevenston, immediately under the vegetable 

 soil, is a bed of shingle, in which forty-seven species of shells com- 

 mon on the adjacent shores have been found. It rests upon shale 

 perforated in many places by the Pholas crispata, of which the shell, 

 in a very friable state, is generally found within the cavity. 



At Largs the shore rises to the height of t^venty feet above high 

 water. Under a bed of loam, from five to ten feet above the sea- 

 level, is a sandy stratum one foot thick, from which Mr. Lands- 

 borough has obtained specimens oi Millepora polymorpha, and seventy 

 species of marine shells, the whole of which are well-known inhabit- 

 ants of the British seas, except two species of Rissoa, one of which 

 had been previously found only in the crag, and the other is referred 

 with doubts to the Rissoa Harveyii of Mr. Forbes. 



Respecting the age of this deposit, Mr. Landsborough states, that 

 IGO species having been found in it by Mr. Smith and other geolo- 

 gists, it would be rash to infer from the above two exceptions, " that 

 there is a difference in the faunas of the existing period of sea-level 

 and of that which preceded it ;" but he thinks it is not improbable 

 that some change may have taken place during the very long period 

 in which the inland cliff was formed by the slow wasting of the sea ; 

 and he adds, the position of the bed at Largs, being ten feet under 

 the surface, indicates a considerable antiquity, although its age must 

 be much newer than that of the Pliocene strata, in which there is a 

 decided proportion of extinct Testacea. 



Lists of the shells found by the author at each locality accompany 

 the paper. 



"Notes by Mr. Maclauchlan, F.G.S., to accompany some Fos- 

 sils collected by himself and Mr. Still, F.G.S., during their employ- 

 ment on the Ordnance Survey in Pembrokeshire." 



Taking for a base-line the northern boundary of the Llandeilo 

 flags laid down by Mr. Murchison, the author proceeds to describe 

 a section extending from near Llanhuadaiu on the south, to Dinas 



2 L 2 



