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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



to forty miles. The list of marine invertebrate animals, both radiata, 

 mollusca, and articulata, is by no means inconsiderable, but very few 

 traces of any vertebrate animal were found. When these occurred, 

 (in five or six cases only), they were limited to fish, consisting of a 

 few ear-bones, as in the Crag, and of small vertebrae. No cetaceans 

 were met with, no relics of terrestrial mammals, although at some 

 points they approached near to the shore so as to dredge up a few 

 fragments of wood. In two or three instances only were any articles 

 of human manufacture, such as a glass bottle, fished up. If reliance 

 could be placed on negative evidence, we might deduce from such 

 facts, that no cetacea existed in the sea, and no reptiles, birds, or 

 quadrupeds on the neighbouring land. 



One solitary helix, which had been carried out to sea by a hermit 

 crab, was brought up from a depth of six fathoms ; but no freshwater 

 mollusca were obtained, probably because their shells are in general 

 very fragile. 



The absence even in the coal-measures of land-shells is a singular 

 and, if I mistake not, significant fact. The known living species of 

 the genera Helix, Cyclostoma, Bulimus, Achatina, Pupa, and Clau- 

 silia exceed 2000 in number ; and not one of these genera, nor any 

 of the pulmoniferous mollusca, such as Lymneus, Planorbis, Physa, 

 &c, have as yet been detected in any one of the primary strata from 

 the Silurian to the Permian inclusive. Yet no one who reflects on 

 the great number of palaeozoic marine shells, and the extent to which 

 they can be arranged under the genera or families established for the 

 classification of recent testacea, can reasonably doubt that the lands 

 of those periods were also inhabited by mollusca. 



Some few shells of the coal-measures have been referred to the 

 genus Unio, and others to an annelid allied to Spirorbis, and called 

 Microconchus, probably an inhabitant of brackish water. That other 

 land and freshwater shells should be so rare as hitherto to have 

 escaped detection surprises me the less when I remember how dili- 

 gently I searched in vain in the alluvial strata laid open in the delta 

 of the Mississippi at low-water for similar remains. In some of the 

 ancient fluviatile mud of the valley of the Mississippi, which I have 

 compared to the loess of the Rhine, land and freshwater shells of ex- 

 isting species abound, but they must be extremely scarce, in the low 

 region of cypress-swamps, near the sea, where we behold conditions 



