A. R. Andrew—The Dolgeliey Gold-belt. 159 
broad, while on the outer half they are mostly very fine. The carinal 
portion, instead of being ornamented with slightly flattened longi- 
tudinal ridges, has extremely fine longitudinal lines. It differs 
further in other characters, the most important being that the scutal 
margin is sinuous, while it is practically straight in S. dess¢mile. 
S. dissimile may also be compared with the tergum from the 
Cenomanian (Korytzaner Schichten) of Kamajk, Bohemia, represented 
in the figure given by J. Kafka! (1886), and assigned by him to 
S. tuberculatum, Darwin. This tergum agrees in having a number of 
raised longitudinal ridges radiating from the apex, but disagrees, 
among other characters, in that the valve is not conspicuously divided 
into two parts by a prominent ridge, and in the absence of a groove 
extending from the apex to the scutal margin. 
In conclusion I wish to thank the following gentlemen for help in 
connexion with this paper: Dr. F. A. Bather, Mr. C. P. Chatwin, 
Dr. A. W. Rowe, and Mr. C. Davies Sherborn. 
1V.—Tue Geronogy oF tHE DoterttEyY Gorp-BeLtt, NortnH WaAtEs. 
By Artuur R. AnprEw, M.S&c., F.G.S. 
1. Introduction. 6. History and Statistics of Mining. © 
2. Previous Literature. 7. Lodes of the Dolgelley Gold-belt. 
3. Stratigraphy. 8. Summary of the Veins. 
4. Structure. 9. Genesis of the Auriferous Veins. 
5. Petrology. 10. Bibliography. 
INTRODUCTION. 
fq\HE town of Dolgelley lies slightly outside the main tract of gold- 
bearing country of Merionethshire, but it forms a convenient 
headquarters from which to visit the various gold-mines and auriferous 
lodes. The Dolgelley Gold-belt lies within the area covered by the 
quarter-sheets 27 N.E., 278.E., 32 S8.E., 33 N.W., 33 N.E., 338.W., 
36 N.W., 36 N.E. of the 6 inch Ordnance Survey maps of Merioneth- 
shire. It is on the north side of the estuary of the Mawddach, 
extending from the sea at Barmouth to the locality of Gwynfynydd 
on the north-east. ‘The belt forms the south-eastern flank of a range 
of high ground sloping down to the south and south-east from the 
mountains of Rhinog, Diphwys, and Garn. It is drained by several 
tributaries of the Mawddach, of which the principal are the Afons 
Hirgwm, Cwm-llechen, Cwm-mynach, Wnion, Las, Gamlan, Eden, 
and Gain. 
The rocks of the Gold-belt all belong to the Cambrian System, and 
are of two main lithological types— 
(1) The greywacke set of the Harlech Grits of H.M. Geological 
Survey. 
(2) The shale set of the Lingula Flags of H.M. Geological 
Survey: the lowest bed of the latter is usually separated out as 
a distinct zone, the Menevian. 
Previous Lirrrature. 
A considerable amount of literature has accumulated, dealing with 
the stratigraphy, paleontology, petrology, mineralogy, and also the 
1 «¢ Prispevek ku poznani cirripedi Geského ttvaru kfidového’’: Sitz. Ber. k. 
Bohm. Ges. Wiss., Prag, 1885, p. 565, pl. i, fig. 7. 
