﻿144 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



points of which protrude a little to the N.E. of this locality. Here 

 the Silurian strata consist of very fine-grained, slightly micaceous, 

 dark-grey sandstone, separated by thin wayboards of greenish shale. 

 Fossils abound, and for the most part their shells are so well pre- 

 served, that great was my astonishment when I cast my eye over the 

 surfaces of this rock and thought of the long time which had elapsed 

 before such unequivocal and really beautiful Silurian types had been 

 made known in Scotland. 



Among the fossils, the Atrypa hemisphcerica, Sow. (Sil. Syst.), is 

 most abundant, and is associated with the Orthis elegantula, Dalm. 

 {canalis, Sow., Sil. Syst.), 0. reversa, Salter, and Strophomena 

 pecten, Dalm. Of Trilobites there is a large, but imperfect Illcenus, 

 the Phacops Stokesii (P. macrophthalma of Sil. Syst.), and small 

 fragments of Calymene Blumenbachii ; an Orthoceratite with very 

 close septa ; Turritella obsoleta (Sil. Syst.), Bellerophon dilatatus 

 (Sil. Syst.), Murchisonia, Turbo, and a Trochus (T. Moorei, M'Coy). 

 There are two species of Encrinites, and several forms of Corals, inclu- 

 ding the Petraia (or Turbinolopsis) subduplicata, M'Coy, P.cequisul- 

 cata, M'Coy, and perhaps P. elongata, Phill., so abundant in the 

 Lower Silurian rocks of Caermarthenshire and other places, together 

 with the well-known Porites pyriformis, Lonsd.*, Favosites alveolaris 

 or Gothlandicus, Sil. Syst., and Ptilodictya (Stictopora) acuta, Hall. 

 There is also a singular unpublished body (PI. IX. figs. 16, 17), which 

 Mr. Salter, to whom I referred all my collection, recognises as identical 

 with a fossil of the Llandeilo flags of Robeston Wathen in Pem- 

 brokeshire, and which may either be the flattened nidus or egg- 

 capsules of a Gasteropod, or a new form of Bryozoon. 



In the continuation of this line of low hills at Lower Thrave, Snaid, 

 &c, this shelly sandstone has usually an ochreous red colour, contain- 

 ing the Lichas laxatus, M'Coy, which is common in the Llandeilo 

 limestone of South Wales, in its equivalent the Bala limestone of North 

 Wales, and in Ireland ; together with Atrypa hemisphcerica, Sow., 

 var., Hemithyris angustifrons, M'Coy, Orthis reversa, Salter, O. bifo- 

 ratus, Schloth., Phacops Stokesii, common in May Hill, Gloucester- 

 shire, and the Terebratula cuneata, Dalm. The presence of this last- 

 mentioned Wenlock fossil, which has not yet been found in the Lower 

 Silurian rocks of England, coupled with other fossils which usually 

 pertain to higher members of the series, including the Phacops Stokesii 

 of Dudley, might lead one to suppose that these shelly sandstones 

 are, as a whole, the upper part of the Lower Silurian rocks. On the 

 other hand, some of the forms point clearly to the horizon of Llandeilo, 

 a position to which Mr. Salter would rather refer them. 



In crossing the Mulloch Hill to the N. and by W., the above- 

 mentioned sandstones are seen to graduate downwards into partial 

 conglomerates, in which fragments of red granite, limestone, and 

 other rocks occur, and the whole, then folding over in gentle undu- 



* This fossil, it would appear, must change its name ; Mr. Dana proposes to re- 

 store Guettard's old name Fleliolites for the genus, and Wahlenberg's specific name 

 interstinctus might stand for the species, or more properly still subrotundus of 

 Fougt. Prof. M'Coy proposes the name Palceopora for the genus. — J. W. S. 



