184 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 20, 



of Kirkcudbrightsliire. These beds appear to have been deposited 

 in a shallow sea ; no fossils have yet been found in them. 



In the Lower part, similar shales and thin flaggy sandstones. 



The calcareous nodules in the upper shale have afforded at Gipsey 

 Head the fossils already noticed in the Society's Journal * ; and in one 

 of the shale beds with nodules, at the N.W. side of Big Raeberry, 

 numerous specimens of Orthocerata, in a more or less fragmentary 

 condition, occur, together with broken shells of Terehratula arid 

 Orthis, and Crinoidal rings. These remains generally lie in close 

 proximity to thin wavy courses of sandy particles which run through 

 the shale, and appear to have been left by the silurian sea in the 

 hollows of the rippled mud. The shell fragments have a bleached 

 aspect, and altogether the character of this deposit has reference to 

 sea-beach conditions. (See Ann. Nat. Hist. 2 Ser. vol. iii. p. 1 56.) 



No. 2 consists of greywacke sandstone ; the lower part thick- 

 bedded. No fossils were found in it. 



No. 3 consists of indurated black shale with Graptolites. Grap- 

 tolitJms priodon, Bronn, and G. Flemingii, Salter, are found at Mul- 

 lock Bay ; and Orthocerata with Gi'aptolites, at Brandy Craig. 



A little south of Long Robin is the most northerly point at which 

 the author met with the graptolitic shale. 



Along the coast from Netherlaw Point to Bahnae Plead (Gipsey 

 Point), these rocks occur in highly inclined and vertical beds, and 

 appear to form two or more synclinal troughs, which have a nearly 

 east and west direction. From Balmae Head northward, for about 

 two miles along the east side of Kirkcudbright Bay, the coast-section 

 traverses six or more synclinal troughs, parallel to the former, con- 

 sisting of the greywacke sandstone and graptolite shale, which under- 

 lie the shales and sandstones of No. 1. 



Throughout all this line of coast the Silurians are traversed by 

 vertical dikes of porphyries and amygdaloidal traps, the general di- 

 rection of which is about N.E. and S.W. One porphyry dike, how- 

 ever, occurring at intervals on the face of the cliff along the east side 

 of the Bay, appears to have had a sinuous N. and S. direction. 



The origin of the flexures into which all the strata have been 

 thrown is in part the intrusion of the dikes of porphyry, &c., intersect- 

 ing the Silurian rocks of this districtf . There must, however, have 

 been some other cause, combined with these dikes, which is not ap- 

 parent, and which acted laterally, in order that a succession of flexures, 

 such as are here noticed, should have been produced. 



Of the thickness of these rocks, owing to the contortions of the 

 beds, even an approximation can scarcely be arrived at. 



This series of deposits constitute the Upper Silurians, — as they 

 occur between Netherlaw Point, at the western extremity of the 

 Parish of Rerwick, and the Cutters Pool, in the Estuary of the River 

 Dee. These, however, are not the sole representatives of this por- 

 tion of the silurian formation in this neighbourhood. The Island of 

 Little Ross, on the western side of the entrance into Kirkcudbright 



* Vol. iv. p. 206 ; and vol. vii. p. 54. 



t See also Quart, Journ. Geol. Soc. vol. vii. p. 56. fig. 2. 



