Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 26 MOLLUSCA. and it is only later, from the third year onwards, that they become females produce ova. Moebius. on the contrary, asserts that the sperm is the later formed, and not until after the pregnant beast has got rid of her eggs. The re- production takes place especially in the months of June and July, at which time, in spite of their extraordinary fertility, the oysters must not be gathered. 0. crixta. ijaUi Ohemn., in the Indian Ocean. A/tumia epliippntm L. Pltii-mni placen
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 26 MOLLUSCA. and it is only later, from the third year onwards, that they become females produce ova. Moebius. on the contrary, asserts that the sperm is the later formed, and not until after the pregnant beast has got rid of her eggs. The re- production takes place especially in the months of June and July, at which time, in spite of their extraordinary fertility, the oysters must not be gathered. 0. crixta. ijaUi Ohemn., in the Indian Ocean. A/tumia epliippntm L. Pltii-mni placenta L. Fam. Pectiniiae. Scollops. Shell equivalved or unequivalved, but tolerably cquisided, with straight hinge line ; often with fan-shaped ribs and bauds, with single adductor muscle. The free and completely split mantle edges bear numerous tentacles, and often emerald green eyes in great number. The small foot often secretes byssus fibres for attachment. Some are attached by their arched shell valve (Spondylns). others swim about by rapidly opening and closing the shell (Prcten). Many are edible and are even more esteemed than Br FIG. 504.—Mi/til us tiliilh (regne animal). O, mouth; s, labial palps; P, foot; S, byssus secretion; Br, gills; M, thickened edge of mantle. i the oysters. Pecten Jacoba-iis L., P. P. varinx L. Mediterranean. Spondylus gaederopiis L. Lima sqiianioxtt Lam. Fam. Aviculidae. With oblique unequivalved shell of laminated texture and inner mother-of-pearl layer. They possess two adductor muscles, of which, however, the anterior is very small. Mantle completely open. Foot small, secreting byssus. Ariciila hit-undo Gulf of Tarent. Meleagrina margari- tifera L., pearl mussel, inhabits especially the Indian and Persian Oceans, and also the Gulf of Mexico. Secretes pearls.* The internal layer of the shell is used in commerce as mother-of-pearl. Malleus mli/nrix, Lam., Indian Ocean. Fam. Mytilidae (fig. 504). Mussels. Shell equivalved, c
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