OCR Text |
Show 1878.] AND DISTRIBUTION OF THE CRAYFISHES. 767 Chceraps (?). I. The outer face of the podobranchia of the antepenultimate thoracic limb of the left side (X 3). II. The inner face of the same podobranchia: B, basal portion; st, stem ; al, ala; br, branchial filaments. III. A transverse section of the middle of the podobranchia (X 3). IV. A sickle-shaped hook of a branchial filament T 4 W of an inch in length. V. One of the coxopoditic setae more highly magnified: a, the circumferential inflexion of the wall of the seta. The central canal does not stop at this point, but is continued to the end of the seta. VI. A bundle of coxopoditic setse ( X 3). VII. The extremity of one of the long seta? of the posterior edge of the stem. The vertical line represents -j-^ of an inch magnified to the same extent. |