. Text-book of zoology for schools and colleges. Zoology. CRUSTACEA. 133 weed, in cracks of rook, or in pools near the line of low water. Some of them, however, can swim with tolerable activity, and some of them (the land-crabs) even live habitually inland. One group, the " pea-crabs," is distinguished by the singular habit of living semi-parasitically within the shells of bivalve moUusks, such as the great horse-mussel. The young or larval crab is exceedingly unlike the adult, and has a long and well-developed abdomen, thus approximat- ing to the type of structure which is permanent
. Text-book of zoology for schools and colleges. Zoology. CRUSTACEA. 133 weed, in cracks of rook, or in pools near the line of low water. Some of them, however, can swim with tolerable activity, and some of them (the land-crabs) even live habitually inland. One group, the " pea-crabs," is distinguished by the singular habit of living semi-parasitically within the shells of bivalve moUusks, such as the great horse-mussel. The young or larval crab is exceedingly unlike the adult, and has a long and well-developed abdomen, thus approximat- ing to the type of structure which is permanently retained in the Macrura. Oedee Isopoda (Gr. isos, order are a number of Crus- taceans of which some in- habit the sea, others are parasitic in their habits, and others are terrestrial. The best known are the common wood-lice {Oniscus, Fig. 52), which are found so com- monly under stones, or in the crevices of old walls. The Isopods all belong to a group of Crustaceans in which the eyes are not sup- ported upon stalks, and they are therefore said to be " ses- ; The head is dis- tinct from the segment bear- ing the first pair of feet. The thoracic feet are all similar to one another, and the bran- chiae are developed on the abdominal legs. equal; pocks, feet).—In this. Fis. 52.—Isopoda. Wood-lice (Omsoto). Oedee Mbeostomata.—In this order are only the living king-crabs (Limulus), and some large extinct forms nearly allied to them. They are all distinguished by the fact that the appendages which are placed round the mouth act by their bases as jaws, but have their extremities developed into swimming-paddles, walking-feet, or nipping-claws. The King-crabs or Horseshoe crabs (Fig. 53) constitute a special group called Xiphosura (Gr. xiphos, a sword; and 1. 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
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
