Royal Physical Society. 7 



and figured by Sowerby ; but there are several which appear to be new. 

 The most abundant organisms are the Pectens, of which there are at least 

 three species. Other fossils are the Pentacrinites, Plagiostoma, and 

 Terebratula, of each of which there are several species' — Gryphcea in- 

 curva, and G. Maccullochi ; Pinna, probably of several species ; Belem- 

 nites, Ammonites, at least four species ; Serpulos, &c. The state of keep- 

 ing of the fossils varies considerably in the different beds. The ammo- 

 nites exist, in some cases, as mere flattened impressions. Generally they 

 present only the outer ring, the central portion of the disc having entirely 

 disappeared. In not a few of the layers the condition of the organic re- 

 mains seems to indicate protracted maceration — a conclusion rendered 

 probable by the abundance of casts of the more tender species. The 

 western coast of Skye, along the shores of Loch Slapin, presents a rich 

 field of study to the geologist. The lias, for the space of several miles, 

 is traversed in all directions by dykes and veins of basalt. In some 

 places the limestone is black ; in others, of different shades of gray ; while 

 inland, towards Kilchrist, it takes a snowy white ; but in all cases it has 

 been altered into a compact marble. A series of specimens upon the 

 table exhibits the passage of a calcareous shale, abounding with Gryphaea 

 and Pecten, into a hard fossiliferous limestone, which in turn shades off 

 through various hues of black and gray into a white crystalline marble, 

 destitute of organic remains. The latter rock, as it lies in the quarries 

 at Kilchrist, is not much inferior in colour to the best stone of Italy, 

 though, after being cut and exposed for a few years to the air, it acquires 

 a dirty yellowish tinge. The trap dykes are themselves a curious subject 

 for investigation. Owing to the decomposition of the marble around 

 them, some of large size are seen running up the hill sides like walls. 

 Indeed, when two or three cross each other, the appearance presented 

 reminds one of some ruined relic of the feudal times. Others may be 

 found insinuating themselves among the cross rents of the contorted strata, 

 and terminating in a point as fine as that of a pen. The shores of Loch 

 Slapin are, on the whole, one of the most interesting localities in the 

 island ; and a careful examination of them would form a valuable contri- 

 bution to Scottish geology. The district lies far out of the ordinary track 

 of the tourist, and the accommodation, where it can be had, is not of the 

 best ; but these disadvantages would doubtless be more than compensated 

 by a ramble among the beautiful sections which abound in the creeks and 

 caves of that solitary shore. 



IV. On some Worm Tracks in Silurian Slates. By Alex. Bryson, Esq. 



Mr Bryson showed that considerable difficulty was felt in accounting 

 for these curious appearances on the Silurian slates at Thornielee, Peebles- 

 shire. They had been named by Professor M'Coy Crossopodia Scotica, 

 or fringe-footed animals. Sir Roderick Murchison described them as 

 occurring of considerable length, even extending to yards. Mr Bryson 



