80 REPORT—1863. 
sand, taken from any spot beyond the reach of fluviatile action, some ma- 
rine débris may be found. Having these facts and some experience to 
guide us in the inquiry, I think we ought not to call any strata which are 
unfossiliferous marine, unless there are sufficient grounds for supposing that 
the absence of fossils is caused by chemical absorption or decomposition. 
The subjoined Appendix will show the additions made to the list of British 
Mollusca in consequence of the Shetland dredgings. 
Mr. Norman and Mr. Brady will give in subsequent papers the results as 
regards other departments of the marine Invertebrata; and we hope to com- 
plete and publish next year a full catalogue of all the species. 
I submitted to the inspection of Mr. Prestwich a sample of small gravel 
dredged up from 85 fathoms, and about 25 miles off Unst; and that eminent 
geologist has favoured me with the report which will be also found appended 
to thiscommunication. One of these specimens deserves especial notice. It is 
& piece of conglomerate, composed of granitic and other fragments cemented 
by carbonate of lime. There is no calcareous rock within a considerable 
distance from the spot where this piece of conglomerate was found, It may 
be doubted whether the cement could have arisen from the re-solution of 
dead shells. The probability is that the specimen in question may have 
been carried during the glacial epoch by an iceberg or coast-ice from Nor- 
way. I have a large mass of conglomerate, composed principally of recent 
shells of a southern form, which was dredged between Jersey and the oppo- 
site coast of France; but this may haye been formed by a submarine spring, 
charged either with carbonate of lime derived from the underlying chalk, or 
with carbonic acid sufficiently strong to dissolve any calcareous matter within 
the range of its action. The shells contained in the last-mentioned piece of 
conglomerate have not undergone any dissolution. I agree with Dr. Wal- 
lich as to the probability that “‘the demand for carbonate of lime at the 
bottom of the sea is limited only by the supply,” and that there is no evi- 
dence of supersaturation as regards a material so essential to the construc- 
tion of shells and similar organisms. For the elucidation of such minor pro- 
blems as this we invite the attention of chemists and geologists, 
APPENDIX. 
Moxtvsca. 
1. Species found in Shetland, and added to the list since the publication of 
Forbes and Hanley’s work. 
Pectenaratus, Gmelin. (P. sulcatus, Mill.) | Rissoa Jeffreysi, Waller. 
Lima Sarsii, Lovén. Odostomia minima, Jeffreys. 
Leda pernula, Miiller. Aclis Walleri, Jeffreys, MS. 
Limopsis aurita, Brocchi. Eulima stenostoma, Jeffreys. 
Arca nodulosa, Miiller. Cerithiopsis costulata, Moller. (Cerithium 
A. obliqua, Philippi. (A. Korenii, Daniels- niveum, Jeffreys.) 
sen. ? aperta, Jeffreys (as Recluzia aperta). 
Newra rostrata, Chemnitz. Pleurostoma nivale, Lovén. 
Cleodora infundibulum, 8. Wood. Cithara haliaéti, Jeffreys, MS. 
C. pyramidata, Zydoux and Souleyet. Fusus Islandicus, Chemnitz. 
Dentalium abyssorum, Sars. Scaphander librarius, Lovén. 
Margarita maculata, 8. Wood. (M.elegan- | Cylichna alba, Brown. (C. triticea, Cou- 
tula, Jeffreys, MS.) thouy.) 
2. Species unknown elsewhere, either as recent or fossil, 
Jeffreysia globularis, Jeffreys, 
