Elementary text-book of zoology. Special part: Mollusca to man / by C. Claus ; translated and edited by Adam Sedgwick ; with the assistance of F.G. Heathcote.
- Carl Friedrich Wilhelm Claus
- Date:
- 1897
Licence: Public Domain Mark
Credit: Elementary text-book of zoology. Special part: Mollusca to man / by C. Claus ; translated and edited by Adam Sedgwick ; with the assistance of F.G. Heathcote. Source: Wellcome Collection.
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![most Cephalophora (Odontophora) a large muscular mass, the tongue, covered by a hard chitinous plate, the radula, is found upon the floor of the buccal cavity. The heart, on the other hand, more nearly resembles in structure and position that of the Lamellibranchs, in that it consists of two auricles opening into a median ventricle, which lies over the rectum. The kidneys are paired, and open right and left in the mantlo furrow; [they also open, as in other Molluscs, into the pericardium]. The Placophora are dioecious. Testes and ovaries are simple unpaired glands, which lie im- mediately over the liver and alimentary canal; their ducts open on each side into the mantle cavity in front of the kidneys. The development of the egg begins with an equal segmentation; subsequently the segments of one-half of the ovum divide less rapidly. This half is invaginated, so that a gastrula arises. The larva which leaves the egg membranes resembles Loven’s worm larva in the possession of two eye-spots and a ciliated ring, and develops without a larval shell. Fam. Chitonidae. In place of the shell, eight calcareous pieces arc present, which are so arranged that the hinder edge of one shell piece overlaps the anterior edge of the next following piece. Chiton squamosus L., Mediterranean. Cryptocliiton Stellcri, Midd. Sub-order 2. Cyclobranchiata. Prosobranchiata with flat plate- sliaped shell and foliaceous gills, which are arranged in a closed circle under the edge of the mantle round the broad root of the foot. The buccal lobes are little developed. The foot is powerful, and usually flat and broad. The lingual armature, like that of the Placophora, is formed of toothed horny plates, hence the name Docoylossa of Troscliel. A cervical gill placed on the right side of the neck is sometimes present (Lottia). Two kidneys are present. External copulatory organs absent. They feed on plants. Fam. Patellidae. (Limpets). The shell is bowl-shaped, and consists of a single piece, to which the animal is attached by a horse-shoe-shaped muscle. Head with two tentacles, at the swollen base of which arc placed the eyes. Tongue extraordinarily long and spirally coiled. Tbc radula is without the median plates, while the intermediate and marginal plates arc raised to hooks, and smaller lateral plates appear. Patdla L. The apex of the shell is slightly eccentric, and hardly inclined to the front. P. cceruh'a L., P. tarentina Lam., P. scutellaris Lam., Adriatic and Mediterranean. ATacella Sehum. Circle of gills broken on the head; the apex of the pellucid shell, shining internally like mother-of-pearl, bent forwards. . N. pelhicida L. Sub-order 3. Zeugobranchiata. Gills bipennate, paired and sym](https://iiif.wellcomecollection.org/image/b2813378x_0047.jp2/full/800%2C/0/default.jpg)
