Cox, Coxa or basal segment of the ex', The exopodite of the sixth leg.
All the appendages are pediform and bi-ramose; all have a prominent gnathobase, and in all the exopodite carries a comb-like series of secondary processes.
Thus, in the thoracic limbs of the Malacostraca, the endopodite generally forms a walking-leg while the exopodite becomes a swimmingbranch or may disappear altogether.
The two distal endites are regarded as corresponding to the endopodite and exopodite of the higher Crustacea, the axis or corm of the Phyllopod limb representing the protopodite.
It is not altogether easy to recognize the homologies of the endites and exites even within the order Phyllopoda, and the identification of the two distal endites as corresponding to the endopodite and exopodite of higher Crustacea is not free from difficulty.
(Fritz Miller.) and exopodite persisting only as sensory " palps " or disappearing altogether.
In the Malacostraca, the antennules are often biramous, but there is considerable doubt as to whether the two branches represent the endopodite and exopodite of the other limbs, and three branches are found in the Stomatopoda and in some Caridea.
In the Malacostraca they are chiefly sensory, the endopodite forming a long flagellum, while the exopodite may form a lamellar " scale," probably useful as a balancer in swimming, or may disappear altogether.
In most cases, however, the palp loses its exopodite and it often disappears altogether, while the coxal segment forms the body of the mandible, with a masticatory edge variously armed with teeth and spines.
The endopodite, when present, is unsegmented or composed of few segments and forms the " palp," and outwardlydirected lobes representing the exopodite and epipodites may also be present.
Protopodite, endopodite, exopodite, and epipodite were considered to be the morphological units of the crustacean limb.
A second ramus, the " exopodite," often is also retained in the form of a palp or feeler.
(4) Three of the rami of the primitive limb (endites 5 and 6, and exite I) specially developed as endopodite, exopodite, and epipodite - the first two often as firm and strongly chitinized, segmented, leg-like structures; the original axis or corm reduced to a basal piece, with or without a distinct gnathobase (endite i)- typical tri-ramose limb of higher Crustacea.
En s, The rudimentary sixth endite (exopodite of higher Crustacea).
(6) Two rami developed (usually, but perhaps not always, the equivalents of the endopodite and exopodite) supported on the somewhat elongated corm (basal segment).