An Introduction to Geology, and Its Associate Sciences; Mineralogy, Fossil Botany and Conchology, and Palaeontology
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. 1851 edition. Excerpt: ... The shell is lined with a vascular membrane called the mantle, which surrounds the body and secretes the shell. The animal is attached to its calcareous envelope by one or more muscles to close the valves and antagonise the elastic ligament of the hinge, which constantly tends to open them asunder. The animal has no head; the mouth is situated at the anterior part of the body and is surrounded by fleshy lips. It opens into a short oesophagus which leads into a stomach and intestine of various lengths, and terminates in an anus. There is a large glandular liver for secreting bile, which is poured by numerous ducts into the digestive tube. Circulation is accomplished by arteries and veins, aided by a symmetrical two-chambered heart; the ventricle of which in some genera surrounds a (part of the intestine, the rectum. Respiration is performe by four equal-sized branchial leaflets distinct from the mantle, and arranged symmetrically on each side of the body. The nervous system consists of ganglia, situated at the anterior and posterior parts of the body, from whence nerves proceed to the labial organs, the adductor muscles, branchiae, viscera, mantle, and foot. In the pecten a number of bright little ocelli, or e es, like small emeralds, are set round the free margin of the mantle. These organs of vision are found in several genera of the class, as area, caraliwm, &c. The shell consists of the hardening material, the carbonate of lime, deposited in an organised gelatinous cellular membrane. The forms of the cells and structure thereof vary in the different families. The animal membrane and earthy matter are arranged in successive layers, the number of which increases with the growth of the mollusc, the largest and outermost being the last...
- Paperback | 150 pages
- 189 x 246 x 8mm | 281g
- 28 Jun 2012
- Miami Fl, United States
- Illustrations, black and white