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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



Cheirurus (Amphion) gelasinosus, Portlock, sp., PI. VIII. fig. 1. 



Heliolites (Palseopora) favosus, M'Coy. 



Favosites alveolaris, Blainv. sp. 



Petraia (Turbinolopsis) elongata, Phill. sp. ? 



Encrinites, &c. 



Coupling these and the Maclurea macrompkala, M'Coy, found also 

 by Professor Sedgwick in this quarry, with the large Illcenus in the 

 adjacent sandstone of Mulloch Hill, there can be no doubt that both 

 these rocks belong to the same zoological group of the Lower Silurian 

 rocks. At one end this rock is flanked by a coarse pebbly conglo- 

 merate, and this again by schist. The latter is cut through by a 

 magnificent dyke of greenstone, which has been extracted for the 

 use of the roads, leaving the indurated schist as walls on either 

 side of a profound and slightly tortuous channel of about 60 feet 

 deep, 150 feet long, and 12 feet wide. 



1 could not look at the mineral character of this mass of limestone, 

 nor at its association with pebble beds and trap rocks, and not have 

 the analogy of the Nash Scar and old Radnor limestones of the Silu- 

 rian region forcibly brought to mind ; and, if the above-mentioned 

 fossils had not been found, the two rocks might have been rudely 

 assimilated. For my own part, however, the more I have seen of 

 the rocks of this age in other countries distant from each other (and 

 even in the Silurian region I showed the evanescence of the test), 

 the less I am disposed to adhere minutely to divisionary lines, as 

 marked by any courses of concretionary limestone. Judging from 

 fossils and the analogy of other parts of this tract, it is indeed almost 

 certain that this limestone of Craig Head lies low in the Scottish Silu- 

 rian rocks, and is here upcast through the shelly sandstone. It is, I 

 have no doubt, the equivalent of other limestones, which, as I shall 

 presently show, have been raised up on other anticlinals further 

 southwards. On the whole, then, there is no doubt that the ridge 

 on the north bank of the Girvan marks the anticlinal No. I of the 

 map. 



Saugh Hill Section. — To the south of Girvan Water the Silurian 

 rocks rise, as before said, into loftier eminences, of which Saugh Hill, 

 nearly 1000 feet above the sea, and immediately to the east of the 

 town of Girvan, is the most prominent. Having made a transverse 

 section of the strata about three miles inland, and another oblique 

 section where the ends of some of them are exposed at low water to 

 the S. of Girvan, I shall be enabled to show the grounds for the 

 conclusions at which I have arrived. 



In ascending from the carboniferous trough about a mile and a half 

 E.N.E. of Girvan, there is first seen a yellowish sandstone which 

 dips 45° S., and thus seems to plunge under the whole mass of Saugh 

 Hill. But this sandstone, in which there is no trace of fossils, is 

 evidently referable to the carboniferous group (c) . The Girvan Water 

 indicates, as before said, the axial line of a valley, from which the 

 carboniferous strata have been thrown off to the south on this side, as 

 they are to the north on the opposite side of the depression above Dal- 



