Text-book of comparative anatomy . FIG. 222.— -•* ~ Boreomysisscyphops 9(after G. ). Thefree portionof the ceph-alo-thoraxcut off at xto show thefree thoracicsegments 77-VIII lyingbeneath withthe branchialfolds br. aul, Cup-shaped ophthalmic lobe without eye (without pigment or visual apparatus);and posterior antennae ; mdt, maudibular feeler ; mx, maxilla:; bj, 1st thoracic foot with exopodite(ex) and epipodite (ep), the latter in the uncovered branchial cavity bl, brood lamella; of tin-2d-Sth removed thoracic feet; a&j, 1st abdominal segment; cth, cephalo-thorax. VOL. I Y. j, «o, anter
Text-book of comparative anatomy . FIG. 222.— -•* ~ Boreomysisscyphops 9(after G. ). Thefree portionof the ceph-alo-thoraxcut off at xto show thefree thoracicsegments 77-VIII lyingbeneath withthe branchialfolds br. aul, Cup-shaped ophthalmic lobe without eye (without pigment or visual apparatus);and posterior antennae ; mdt, maudibular feeler ; mx, maxilla:; bj, 1st thoracic foot with exopodite(ex) and epipodite (ep), the latter in the uncovered branchial cavity bl, brood lamella; of tin-2d-Sth removed thoracic feet; a&j, 1st abdominal segment; cth, cephalo-thorax. VOL. I Y. j, «o, anterior 322 COMPARATIVE ANATOMY CHAP. well-developed masticatory ridges. In contradistinction to the maxillipedes, the 5posterior pairs of thoracic feet are described as ambulatory feet. The Decapoda oweto them their name. They are distinguished by the want of the exopodite, so that the appendage consisting of theprotopodite and endopodite is a simplelimb of 7 joints. The exopodites, how-ever, may be present in larval stages,and in a few cases may be retained asrudiments in the adult. The basaljoint of the ambulatory feet carry gills,which project up into the respiratorycavity. The Dccapodan gills, however,must be described in a special anterior ambulatory feet are oftenchelate ; the first pair are generally verypowerful. In the cray-fish the 3 an-terior pairs of ambulatory feet arechelate ; the most anterior ambulatoryfoot is provided with the well-knownlarge forceps. The Abdominal Feet (Pleopoda) (Fig. 225). The 6 anterior of the 7 ab-dominal segments typically
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
