. Elements of geology. Geology. Fin-. 43. to distinguish the two by good generic characters. But, as a general rule, the fluviatile species are small- er, smoother, and more globular than the marine; and they have never, like the Neritee, the inner mar- gin of the outer lip toothed or crenulated. (See Fig. 41.) A few genera, among which Cerithium (Fig. 42.) is the most abundant, are common both to rivers and the sea, having species peculiar to each. Other genera, like Auricula (Fig. 36.), are amphibious, liv- ing both in freshwater and on land. The terrestrial shells are all univalves. The mos
. Elements of geology. Geology. Fin-. 43. to distinguish the two by good generic characters. But, as a general rule, the fluviatile species are small- er, smoother, and more globular than the marine; and they have never, like the Neritee, the inner mar- gin of the outer lip toothed or crenulated. (See Fig. 41.) A few genera, among which Cerithium (Fig. 42.) is the most abundant, are common both to rivers and the sea, having species peculiar to each. Other genera, like Auricula (Fig. 36.), are amphibious, liv- ing both in freshwater and on land. The terrestrial shells are all univalves. The most abundant genera among these, both in a recent and fossil state, are Helix (Fig. ), Cyclostoma, Pupa, (Fig. 44.), Clausilia, Bulimus (Fig. 43.), and Acha- tina ; which two last are nearly allied and pass into each other. The same may be said with almost equal truth of Pupa and Clausilia. Fia-. 44. Fiff. Bulimus luhricus. Pupa musccrum. Helix plcbrium. All recent; and also fossil from Loess of Riant. Fig. 46. The Ampullaria (Fig. 46.) is another genus of shells, inhabit- ing rivers and ponds in hot countries. Many fossil species have been referred to this genus, but they have been found chiefly in marine for- mations, and are suspected by some concho- logists to belong to Natica and other marine genera. All univalve shells of land and freshwater species have entire mouths ; and this circum- Ampuiiaria giauca, staucc may ofton scrvo as a convenient rule for. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lyell, Charles, Sir, 1797-1875; Gibbes, Lewis Reeve, 1810-1894, former owner. DSI; Merrill, George P. (George Perkins), 1854-1929, former owner. DSI. Philadelphia : James Kay, Jun. and Brother ; Pittsburgh : C. H. Kay & Co.
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Keywords: ., bookauthorlyellcharlessir17, bookcentury1800, booksubjectgeology
