Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 OSTBACODA. 423 Order 2.—OSTEACODA.* laterally compressed Entomostraca, n-'ttli « Ji shell and seven pairs of appendages, which function us antennae, jaws, creeping and surimming legs. There is a pediform mandibular palp, and a short abdomen. The body of these small Crustacea is unsegmented and is completely enclosed in a bivalve shell, which gives the animal a resemblance to a mussel. The two valves of the shell join together in the middle line, and are fastened together by an elastic li
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 OSTBACODA. 423 Order 2.—OSTEACODA.* laterally compressed Entomostraca, n-'ttli « Ji shell and seven pairs of appendages, which function us antennae, jaws, creeping and surimming legs. There is a pediform mandibular palp, and a short abdomen. The body of these small Crustacea is unsegmented and is completely enclosed in a bivalve shell, which gives the animal a resemblance to a mussel. The two valves of the shell join together in the middle line, and are fastened together by an elastic ligament along the middle third of the back. The action of this ligament is opposed by a two- headed adductor muscle, which passes from one valve of the shell to the other and causes impressions discernible from without. The common tendon of the two heads of this muscle lies nearly in the D G F' Fli \ F' NX' SM Ms lid Ob Fiu. 335.—Female Cifjiri* before sexual maturity; the right valve of the shell has been removed, A', A', first and second pair of antenna?; Od, upper lip ; Md, mandible with pediform palp; G, cerebral ganglion with unpaired eye; SM, adductor muscle ; MX', MX', first and second pair of maxilla; F', F', first and second pair of feet; Fit, caudal fork ; If, stomach ; D, intestine ; L, hepatic tube ; Ge, rudimentary genital organs. middle of the body. The edges of the valves are free at both ends and along the ventral side. In the marine Cypridinidce there deep indentation in the edges of the valves, to allow the antenna? to pass out. When the valves of the shell are open, several pediform appendages can be protruded on the ventral side, which enable the animal to move in the water either bv crawling- or by swimming. * O D : If. 10. Strauss-Diirkheim, '• Memoire sur Ics Cypris de la classe cles Crus- taces.' Mem. (hi tl'liixt. Tom VII., 1821. W. Zrnker. •• Monographie der Ostracoden,' Archie, fitr -\(iti/i-i/i' Tom. C.
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