COMPENDIUM OF GENERIC DISTINCTIONS. 



797 



Family. CYMOTHOAD^E. Thorax seven-ringed, free. 

 First five rings of abdomen mostly free. First three pairs of 

 legs (or all) strongly clawed. 



Germs. CvMOTHOA. Antennae nearly equal. Eyes scarcely 

 visible. Last segment of tail in a transverse square. North- 

 ern seas. 



Tribe. EPICARDITA. Males permanently minute, 

 females very large. Antennae rudimentary. Abdomen slightly 

 developed. Feet very short. Mouth adapted for suction and 

 gnawing. In males, body thirteen or fourteen-jointed ; one 

 for head, seven for thorax, rest for abdomen. In females, all 

 segments confused together. 



Family. lONID^E. Abdominal appendages fringe-like. 



Genus. IONK. Male, body narrow and long ; abdomen 

 six-jointed, each joint with a pair of membranous appendages. 

 Two pairs of antenna:. Females, body pear-shaped, flat ; 

 appendages branched. Many seas. 



Family. BOPYRID^E. Abdominal appendages flat and 

 hidden under abdomen. 



Genus. BOPYRUS. Mail with a very small antennae, very 

 short legs ; abdomen with minute false legs. Female un- 

 usually pear-shaped flat, abdomen wide at base. Five pairs 

 of false legs, each with a triangular plate. Most seas. 



Sut-tlass. ENTOMOSTRACA. Shell homy or leathery, 

 in one or more pieces. Branchiae attached to feet or jaws. 

 Feet jointed and fringed. 



Legion. BRANCHIOPODA. Mouth formed for biting; 

 branchiae numerous, attached to feet. Body naked or buck- 

 lered. All feet with branchiae. Two or four-jointed antennae. 

 Eyes one to three. 



Order. PHYLLOPODA. Naked or partly bucklered. 

 Feet eleven to sixty pairs, joints leaf-like, mostly respiratory. 

 Two to three eyes. 



Family. APODIDjE. One pair of short antennae. Two 

 eyes. Sixty pairs of feet. Body composed of many rings, 

 almost wholly covered by shell. 



Genus. APUS. As Family. Ponds. 



Family. BRANCHIOPODID^S. Body naked; two pairs 

 of antennae (lower pair prehensile in male) ; eyes two, on foot- 

 stalks. Eleven pairs of feet. 



Genus. CHIOCEPHALUS. Abdomen nine-jointed; tail with 

 two plates. Lower antennae of male cylindrical, with append- 

 ages at base. Ponds. 



Genus. ARTKMIA. Abdomen long, six-jointed. Lower 

 antennae of male flat and without appendages. Salt-pans. 



Order. CLADOCERA. Head projecting ; body enclosed 

 in double buckler, joined on back. Four to six pairs of feet, 

 their joints cylindrical and leaf-like. Eye one, large. An- 

 tennae two pairs ; lower pair large, branched and used as fins. 

 No palpi on mandibles. 



Family. DAPHNIAD-iE. Upper antennas small; five or 

 six pairs of feet ; enclosed in shell. Intestine straight. 



Suit-family DAPHNIN/C. Five pairs of feet. Lower an- 

 tennae two-branched ; one branch three, the other four-jointed. 



Genus. DAPHNIA. Head produced downwards into a 

 beak. Upper antennae one-jointed, under the beak, small ; 

 lower large. Ponds. 



Genus. MOINA. Head round and blunt. Upper antennae 

 one-jointed, long ; lower antennae thick at base. Ponds. 



Suit-family. SIDING. Six pairs of feet. Lower antenna: 

 two-branched ; a row of spines on edge of large branch. 



Genus. SIDA. One branch of lower antennae three the 

 other four-jointed. Ponds. 



Family. POLYPHEMIDJE. Lower part of carapace 

 empty. Four pairs of feet, not included in carapace. Eye 

 very large. Lower antennas two-branched ; one branch four 

 the other three-jointed. 



Genus. POLYPHEMUS. Head distinct from body. Abdo- 

 men long, projecting from shell. Eye occupying nearly whole 

 head. Ponds and ditches. 



Family. LYNCEID^E. Two pairs of antennae; upper 

 short, lower branched ; each branch three-jointed. Five pairs 

 of legs. One eye ; abdomen jointed. 



Genus. CHYDORUS. Nearly spherical. Beak long, sharp, 

 depressed. Lower antennae very short. Ponds and ditches. 



Legion. LOPHYROPODA. Mouth formed for biting. 

 Branchiae few, attached to mouth. Body either with single or 

 double shield. Not more than five pairs of feet ; joints cylin- 

 drical. One eye. Two pairs of antennae ; one pair for loco- 

 motion. 



Order. OSTRACODA. Body in two-valved buckler; 

 branchiae on hind-jaw. No external ovary. Two or three 

 pairs of feet. 



Family. CYPRID^E. Antennae two pairs; upper with a 

 pencil of long filaments, lower thick and foot-like. One eye. 

 Two pairs of feet. 



Genus. CYPRIS. Lower antennae with pencil of long hairs. 

 Ponds. 



Family. CYTHERID./E. Antennas two pairs; upper not 

 with pencil of filaments. Three pairs of feet. 



Genus. CYTHBRK. Feet not enclosed in shell. Abdomen 

 short. Eye one. Valves in front and behind. Marine pools. 



Genus. CYTHERKIS. Valves of shell oblong; edges par- 

 allel above and below, and toothed or notched. Surface ridged 

 and knobbed. In sand. 



Family. CYPRIDINAD^E. Antennas two pairs, foot- 

 like. Feet two pairs, one always within shell. Eyes two, on 

 footstalks. Abdomen tipped with broad plate. 



Genus. CYPRIDINA. As Family. 



Order. COPEPODA. Body divided into wings; head 

 and thorax bucklered. Mouth with foot-jaws. Feet five pairs, 

 mostly for swimming. Ovary external. 



Family. CYCLOPIDJE. Head and body fused together. 

 Foot-jaws two pairs ; fifth pair of legs very small. One eye. 



Genus. CYCLOPS. Foot-jaws large, strong, branched. Ova- 

 ries double. Ponds. 



Genus. CANTHOCAMPTUS. Foot-jaws small, not branched. 

 Ovary single. Fresh and salt water. 



Family. CETOCHILIDJE. Head distinguishable, but 

 fused to first ring of thorax. Foot-jaws strong ; three pairs. 

 Eyes two. 



Genus. CKTOCHILUS. Foot-jaws not branched. Head 

 with two small pointed appendages. Thorax with six, abdo- 

 men with four segments. Last pair of legs like others. 



Genus. NOTODBLPHYS. Thorax four, abdomen four, seg- 

 ments. Upper antenna; many-jointed ; lower prehensile. 

 Foot-jaws four pairs. Ovary large, within walls of body. 



Legion. PiECILOPODA. Mouth formed for sucking. 

 Foot partly for walking or prehension, partly for swimming. 

 Body mostly enclosed in buckler. All parasitical on fishes and 

 other aquatic animals. 



Order. SIPHONOSTOMA. Mouth with tube which has 

 pointed mandibles Thorax ringed, with several pairs of feet. 

 Foot- jaws large. 



Tribe. PELTOCEPHALA.H&A shield-shaped, with 

 frontal plates and two flattened antennae. 



Family. ARGULID^E. Head like circular shield. An- 

 tennae short, two-jointed. Second pair of foot-jaws modified 

 into suckers. 



Genus. ARGULUS. Oval, flat, transparent, veined ; shell 

 notched on either side in front. 



Family. CALIGID^E. Feet four pairs, with long hairs 

 Antennae flat and two-jointed. Second pair of foot-jaws, not 

 sucking discs. Eyes two. 



Genus. CALIGUS. Thorax two-joints. Small sucking disc 

 on under surface of frontal plates. Fourth pair of feet one- 

 branched, slender. 



Genus. CHALIMUS. Thorax four joints. No sucking disc 

 on frontal plate. 



Family. CECROPID^;. Head like small buckler, with 

 frontal plates. One plate-like appendage on upper part of 

 thorax. Ovaries tube-like and twisted. 



Genus. CECROPS. Thoracic appendage small and rounded. 

 All feet in male ; first three pairs in female for walking. 



Tribe. PACHYCEPHALA.Ke*A small, thick, and 

 blunt. Antennae long, five or six-jointed. 



