A Monograph of the Eocene Mollusca; Descriptions of Shells from the Older Tertiaries of England - Softcover
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1849. Excerpt: ... tinguishes the Pleurotomce; the condition of the outer lip, which is much thickened within, and so strongly arched as to be almost semicircular in form; the deep, wide sinus, which divides the posterior extremity of the outer lip from the suture, and exactly resembles the notch by which the Pseudotomce (a section of the Pleurotomc e proposed by Bellardi) are distinguished; and the elevated, reflected anterior margin of the columellar lip, forming the right wall of the anterior canal. The recent cones, distinguished by the beauty and variety of their colouring, are very numerous: three hundred and sixty-nine species are enumerated by Messrs. Henry and Arthur Adams in the different divisions adopted by those authors; and, excepting two species which are found in the Mediterranean, all are inhabitants of tropical seas, abounding chiefly in those of Asia. They inhabit fissures and holes in rocks, and coral reefs, ranging in depth from low-water mark to thirty or forty fathoms. In a fossil state, the genus first occurs in the upper cretaceous strata. M. Deslongchamps, it is true, has referred to it certain shells from the lias of Calvados, exactly resembling cones in outward form, and which, if the genus were correctly determined, would present the anomaly of the cones not being represented during the long epoch which elapsed between the deposit of the middle has and that of the upper chalk. M. D'Orbigny, however, found, on examination, that the inner whorls were as thick as the outer ones; and from this circumstance he has inferred that the shells in question are not true cones, and he has referred them to Acteonina, a genus peculiar to the Oolitic formations, and proposed by him for certain Acteon-like shells, without teeth or folds on the columella. And thu...
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