COMPENDIUM OF GENEPJC DISTINCTIONS. 



799 



Family. ARMADILLID^E . Oval, capable of rolling up 

 into a ball. Appendages of abdomen not beyond edge. 



Genus. ARMADILLO. Body convex and blunt. Outer 

 antennae seven-joimeil. Last i'also feet with large basal joint. 



Fondly. CYMOTHOAD^l. Thorax seven-ringed, free. 

 First five rings of abdomen mostly free. First three pairs 

 \or all) strongly clawed. 



Genus. OYMOTHOA. Antennas nearly equal. Eyes 

 scarcely visible. Last segment of tail in a transverse square. 

 Northern seas. 



Tribe. JZPICARDITA. Mules 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^!. Abdominal appendages fringe-like. 



Genus IONE. Male, body narrow and long ; abdomen 

 six-jointed, each joint with a pair of membranous append- 

 ages. Two pairs of antennae. Females, body pear-shaped, 

 flat ; appendages branched. Many seas. 



Family. BOPYRID^!. Abdominal appendages flat and I 

 hidden under abdomen. 



Genus. BOPYUUS. Male with very small antennae, very | 

 short legs ; abdomen with minute false legs. Female j 

 unequally pear-shaped, flat, abdomen wide at base. Five 

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



Sub-class. ENTOMOSTRAC A. Shell horny 

 or leathery, in one or more pieces. Branchiae attached to 

 feet or jaws. Feet jointed and fringed. 



Legion. Brancijlopolia. Mouth formed for biting ; branchiae 

 numerous, attached to feet. Body naked or bucklered. All 

 feet with branchiae. Two- or four-jointfd antennas. Eyes 

 one to three. 



Order. PHYLLOPODA. Naked or partly bucklered. 

 Feet eleven to sixty pairs, joints leaf-like, mostly respira- 

 tory. Two to three eyes. 



Family, APODID2E. 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. BKANCHIOPODID.fl3. Body naked ; two pairs 

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

 footstalks. Eleven pairs of feet. 



Genus. CRIOCEPHALUS. Abdomen nine -jointed; tail 

 with two plates. Lower antennae of male cylindrical, with 

 appendages at base. Ponds. 



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

 antennas 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 

 tins. No palpi on mandibles. 



Family. DAPHNIAD^I. Upper antennae small; five or 

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



Sub-family. Daphninae. Five pairs of feet. Lower an- I 

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



Genus. DAPHNIA. Head produced downwards into a | 

 beak. Upper antennas 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. 



Sub-family. Sidinae. Six pairs of feet. Lower antennae 

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



Genus. SlDA. One branch of lower antennae three- the 

 other four-jointed. Ponds. 



Family. POLYPHEMID.3D. Lower part of carapace 

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

 very large. Lower antennae tsvo-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 antennas ; upper 

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

 pairs of legs. One eye ; abdomen jointed. 



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

 dapressed. Lower antennnr very short. Ponds and ditches. 



Legion. lopfjpropoDa. Mouth formed for biting. Branchiae 

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

 shield. Not more than five pairs of feet ; joints cylindrical. 

 One eye. Two pairs of antennas ; one pair for locomotion. 



Order. OSTRACODA. Body in two-valved buckler; 

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

 pairs of fe'it. 



Family. CYPRID^!. Ajitennse two pairs ; upper with a 

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

 Two pairs of feet. 



Genus. CYPRIS. Lower antennas with pencil of long 

 hairs. Ponds. 



Family. CYTHERID^E. Antennae two pairs ; upper not 

 with pencil of filaments. Three pairs of feet. 



Genus. CYTHERE. Feet not enclosed in shell. Abdomen 

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



Genus. CYTHEREIS. Valves of shell oblong ; edges 

 parallel above and below, and toothed or notched. Surface 

 ridged and knobbed. In sand. 



Family. CYPRIDINAD^!. Antennae two pairs, foot-like. 

 Feet two pairs, one always within shell. Eyes two, on foot- 

 stalks. 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. CYCLOPID^l. Head and body fused together. 

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



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

 Ovaries double. Ponds. 



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

 Ovary single. Fresh and salt water. 



Family. CETOCHILID^E. Head distinguishable, but 

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

 Eyes two. 



Gemis. CETOCHILUS. 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. NOTODELPHYS. Thorax four, abdomen four, seg- 

 ments. Upper antennae many-jointed ; lower prehensile. 

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



Legion, ^(trflopolia. 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. P-ELTOCEPHALA.Ue&A shield-shaped, with 

 frontal plates and two flattened antennae. 



Family. ABGTILID^J. 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-33. 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.E. Head like small buckler, with 

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

 thorax. Ovaries tube-like and twisted. 



Genus. UECROPS. Thoracic appendage small and rounded. 

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



Tribe. PACHYCErHALA.B&sA small, thick, and 

 blunt. Antennae long, five or six-jointed. 



Family. ERGASILID^!. Body oval or pear-shaped. 

 Feet very small and branched. 



Genus. NICOTUOE. Antennae slender, many-jointed. In 

 female, thorax enlarged into two wing-shaped lobes. Feet 

 four pairs. 



Order. LERNEADA Mouth for suction. Thorax 

 not jointed, all its organs very small. Males unlike females 



