. Bulletin - United States National Museum. Science. The Asellida^ are mostly fresh-water forms. All the members of the genera, Asellus, , and Civcidotea^ are found in fresh- water streams, wells, pools, and lakes. aA . The species Janirella Bonnier is, however, marine. ANALYTICAL KEY TO THE GENERA OF THE FAMILY a. Mandibles without a palp. Last sis pairs of legs with dactylus ])i-unguiculate. Genus MancaseUus Harger f/. ]\Iandible with a three-jointed palp. h. Eyes present. Body oblong, depressed. Head small, narrower and shorter than first tho- racic segment. Caudal seg
. Bulletin - United States National Museum. Science. The Asellida^ are mostly fresh-water forms. All the members of the genera, Asellus, , and Civcidotea^ are found in fresh- water streams, wells, pools, and lakes. aA . The species Janirella Bonnier is, however, marine. ANALYTICAL KEY TO THE GENERA OF THE FAMILY a. Mandibles without a palp. Last sis pairs of legs with dactylus ])i-unguiculate. Genus MancaseUus Harger f/. ]\Iandible with a three-jointed palp. h. Eyes present. Body oblong, depressed. Head small, narrower and shorter than first tho- racic segment. Caudal segment not longer than broad Genus Asellus Geoffroy I/. Eyes wanting. Body elongate, narrow. Head large, not narrower than first thoracic seg- ment, and longer. Caudal segment much longer than broad. Genus Csecklotea Packard 67. Genus MANCASELLUS Harger. Eyes present. Mandibles without a palp. Last six pairs of legs with dactylus bi-unguieulate. Bod}' broad, depressed. Terminal segment of body broad. ANALYTICAL KEY TO THE SPECIES OF THE GENUS MANCASELLUS. o. Lateral margins of head entire. Mancasellus hrachyurus Harger a'. Lateral margins of head not entire. h. Uropoda shorter than terminal segment of body. c. Uropoda half as long as terminal segment of body. Propodus of first pair of legs armed with two triangular processes. Lateral margins of head with a deep cleft on either side. Mancasellus macroums Garman Uropoda two-thirds as long as terminal segment of body. Propodus of first pair of legs armed with one triangular process or three acute teeth. Lateral margins of head with a large rounded sinus on either side. Propodus of first i)air of legs armed with one triangular process. Sides of sinus on lateral margins of head not (Smith) (V. Propodus of first pair of legs armed with three acute teeth. Sides of sinus on lateral margins of head sometimes meeting. Mancasellus dilata Harger . Uropoda as long as terminal segment of body. c. Propodus of
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