5 o CRUSTACEA OF ALABAMA. 



Artificial Key for the Identification of 

 Alabama Crustacea. 



Key to the Orders. 



I. Less than one-fourth inch long, covered by a bivalved shell enclosing entire animal, which possesses few 

 feet . . . . . . . . . Order Ostracoda. 



II. Less than one-fourth inch long, body, except the head, enclosed in a bivalved, delicately sculptured 

 shell, feet fewer than seven pairs. ...... Order Cladocera. 



III. Of small but not minute size, body enclosed in a concentrically-lined bivalve shell, or, except the 



head, in a thin shell, feet more numerous than seven pairs, foliaceous. 



(One division of) Order Phyllopoda. 



IV. Less than one-fourth of an inch long, body elongate, with slender abdomen terminating in two setose 



stylets, head with many-jointed one-branched swimming antennae, eye single, abdominal segments 

 without appendages, thoracic feet of five pairs. .... Order Copepoda. 



V. Often longer than one-fourth inch, much as above, but with more than five pairs of swimming feet, 

 antennae not used in swimming. . . . (second division of) Order Phyllopoda. 



VI. Animals small, enclosed in a calcareous carapace of several parts, permanently attached by carapace or 

 otherwise. ......... Order Cirripedia. 



VII. Animals of moderate size (one-fourth to one and one-fourth inches long), fourteen pairs of walking 



limbs, two long pairs of antennae, body laterally compressed, eyes sessile. . Order Atnphipoda. 



VIII. Much as above, but body depressed, only one pair of obvious antennae, abdominal appendages often 



in the form of gill plates, eyes sessile. ...... Order Isopoda. 



IX. Head and thorax consolidated, covered by a carapace or buckler, eyes stalked, body more or less de- 

 pressed, abdomen incurved and appressed upon the thorax, feet five pairs. . Order Brachyura^ 

 X. Head and thorax consolidated as above, eyes stalked, feet five pairs, body laterally compressed, abdo- 

 men extended, used in swimming. ...... Order Macroura. 



Key to Families and Genera. 



I. Order Ostracoda. [Only the Podocopa of Fam. Cypndae.] 



A. Abdomen terminating in two long, clawed stylets. 



a. Shell more or less reniform or oval, second maxillae with branchial plate. 



(page 34) Genus Cypris. 



b. Second maxillae without branchial plate. 



1. Second antennae with long seta?, shell high and sub-quadrangular. 



(page 29) Genus Notadromas . 



2. Second antennae with setae shorter than terminal claws, shell elongate. 



(page 31) Genus Candona. 



B. Abdomen terminating in two very short stylets armed with a long seta. 



(page 30) Genus Cypridopsis. 



II. Order Cladocera. 



SUB-ORDER I.— CALYPTOMERA [membrane-clothed.] 



Body enclosed in a bivalve shell. Mandibles truncate below. Maxillae distinct, spiny. Thoracic ganglia 



discrete. 

 Tribe I. — Ctenopoda. 



Feet six pairs, similar, foliaceous, all distinctly branchiate. 

 Fam. 1. — SroiD/E. 



Swimming antennae with two unequal rami, intestine simple. 



