. Zoology : for students and general readers . Zoology. PAL^OGABIDA. 317 peculiar in form aud also ensheathed by arteries, and the peculiar nature of the gills of the abdominal feet, as well as the highly developed system of blood-vessels ; that we are obliged to place them in a subclass equivalent to all the other. Fi^. 269.—A^ Brain and eye of a normal Cambarus from Iowa. B^ The same of the blind craw-lish from Mammoth Cave. Cy Cornea.—Packard, del. Crustacea. It is possible that future research may prove that the Palmocarida should form a distinct class of Arthropods, equivalent on the one
. Zoology : for students and general readers . Zoology. PAL^OGABIDA. 317 peculiar in form aud also ensheathed by arteries, and the peculiar nature of the gills of the abdominal feet, as well as the highly developed system of blood-vessels ; that we are obliged to place them in a subclass equivalent to all the other. Fi^. 269.—A^ Brain and eye of a normal Cambarus from Iowa. B^ The same of the blind craw-lish from Mammoth Cave. Cy Cornea.—Packard, del. Crustacea. It is possible that future research may prove that the Palmocarida should form a distinct class of Arthropods, equivalent on the one hand to the Crustacea and on the other to the Insecta, but from the fact that they breatlie like other Crustacea by external gills, we prefer to retain them as a subdivision of the class of Crustacea. Order 1. Merostomata.—The only living representative of this order is the king-crab, belonging to the genus Limulus, represented in American waters by Limulus Polyphemus Linn., which ranges from Oasco Bay, Maine, to Florida and the West Indies. The body of the king-crab is very large, sometimes nearly two feet in length ; it consists of a cephalo-thorax composed of six segments and an abdomen with nine segments, the ninth (telson) forming a long spine. The cephalo-thorax is broader than long, in shape somewhat like that of Ajjus, with a broad fiat triangular fold on the under side. Above are two large lunate compound eyes, near the middle of the head, but quite remote from each other, and two small com- pound eyes situated close together near the front edge of the head. There are no antennae, and the six pairs of append-. 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 the original Packard, A. S. (Alpheus Spring), 1839-1905. New York : Henry Holt
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1879
