470 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 2, 



with a small rounded variety of the Biplograpsus folium^ generally 

 in an imperfect state. In the same shale Bidymograpsus sextans^ 

 Hall, is found along with the Graptolites already referred to as oc- 

 curring in the anthracite-shale, and also a new form of Rastrites, 

 characterized by the length of its cells, which attain almost an inch 

 in size (see p. 475). Besides these, an orbicular Brachiopod, which 

 Mr. Salter informs me is the Siphonotreta micula, M*Coy, occurs ; 

 this is the only bivalve shell as yet obtained in these low deposits. 

 Separating this black shale from the underlying purple and grey 

 grits is a thin drab-coloured shale, in which no fossils are found. 



In the anthracite-shales (2*) which succeed the black shale, we 

 meet with the same fossils which make their appearance in the flexured 

 beds below (2) ; and above these there is seen another dark-coloured 

 shale (3), also abounding in Graptolites, some of which do not occur 

 in the anthracitic schists, viz. Graptolites Sedgwickii, Biplograpsus 

 folium^ and Rastrites peregrinus. Above this another bed of black 

 shale appears, in which only Biplograpsus teretiusculus occurs. 



Light drab-coloured shales (4) succeed ; these are devoid of fossils, 

 but resemble lithologically the deposit which underlies the thin black 

 fossiliferous shale. Beyond the drab-coloured shales (4) the bed of 

 the stream in the glen above consists of gravel. 



Deposits similar to those above-described are common to many 

 localities in the Silurians of the South of Scotland. They are well 

 seen in the course of the Duffkinnell Burn, in the neighbourhood of 

 Rae Hills, in the parish of Johnstone, Dumfriesshire ; and here they 

 afford many of the fossils just alluded to, as well as a form of Ras- 

 trites new to Great Britain, the R. Linncei, Barr. In this locality, 

 besides the remains of these zoophytes, we have evidence of a more 

 highly organized race of animals. These consist of portions of Crus- 

 tacea. One of them is figured in the Quart. Journ. Geol. Soc. vol. 

 viii. pi. 21. fig. 10, and is named by Mr. Salter Bithyrocaris ? apty- 

 choides. Another, which at first sight was a puzzle to palaeonto- 

 logists, Mr. Salter informs me is a portion of the carapace of a 

 crustacean probably of the same genus, — a genus which has hitherto 

 been found only in the carboniferous formation, principally in coal- 

 shales ; a circumstance supporting the conclusion that the anthracitic 

 schists owe their origin to conditions somewhat akin to those imder 

 which the shales of the coal-measures were formed. 



Among these strata of the South of Scotland, we have as yet seen 

 no organic remains from which we can form any idea as to the origin 

 of the anthracite present in some of the schists ; the fossils already 

 referred to being of animal nature, and occurring in the form of 

 pyritous stains. In one instance, however, in black shales overlying 

 the anthracite-schists, the remains of a Fucoid were found ; and this 

 is probably the lowest position in which distinct tiaces of such remains 

 have been met with in Scotland. On referring this fossil to Mr. 

 Salter, he writes me thus : — " It is, I beheve, a Fucoid ; but that of 

 itself is most interesting, as we have no clear traces of fucoids so 

 low." 



Although the anthracitic schists themselves have not yet afforded 

 this form of fossil, still there are some reasons for inferring that this 



