640 



COMPENDIUM OF GENERIC DISTINCTIONS. 



Sub-class. ENT0Z0A.— Parasitical. Mostly elongated. No 

 special organs of breathing. Found inside living animals. 



Order. STER ELM I NT HA. —Intestine absent in some, vascular 

 iu others. 



Family. CESTOIDEJE.— Body long, flattened, soft. No mouth, 

 head mostly with sucking discs. 



Genus. T.k.via. — Body long, jointed. Head with four suck- 

 ing discs, mostly with beak surrounded with booklets. 



Genus. Bothriocephalus. — Head swollen, with two or four 

 opposite furrows. 



Genus. Echinococcus. — Vesicles single or enclosed in cryst. 

 Many minute Entozoa in interior surface. 



Order. C4:LELMi NTHA. — Intestine in a distinct cavity. 



Tribe. NEMATOIDEA.—fto&y round, elastic. 



Family. STRONGYLIDIDJE.— Mouth at or nearly at end of 

 body, not surrounded with retractile books. Body round, long, 

 and elastic. 



Genus. Strongylus. — Body very long, sharp in front. 

 Mouth round or triangular. 



Genus. Ascaris. — Body sharp at both ends. Head three- 

 valved. 



Genus. Tricocephaia's. — Body thread-like in front, sud- 

 denly thickening behind. 



G< reus. Filaria.— Body very long, tbread-like, nearly equal 

 throughout. Mouth rounded. 



CLASS.-ECHINODERMATA. 



Radiate, shin more or less leathery, having variously- 

 shaped chalky pieces imbedded. 



Sub-class. DITREMATA. — Digestive canal distinct, with two 

 openings; outline of body entire. 



Order. HOLOTHU ROIDEA.— Shell none ; no chalky pieces. 

 Body cylindrical, moving by alternate extension and contrac- 

 tion. 



Family. THALASSEMAD.E.— Proboscis with long, fleshy ap- 

 pendage. No tentacles. Vent at end ot body. 



Genus. Thalassema. — Body cylindrical, rounded and smooth 

 behind. Proboscis short. 



Family. PRIAPULIDiE.— Proboscis retractile. Tentacles 

 none. Vents at end of long tail. 



Genus. Priapulus. — Body blunt behind. Tail branched 

 and pointed. 



Family. SlPUrJCuTJD.ffi.— Proboscis retractile, tentacled at 

 tip. Vent at base. ( 



Genus. Syrinx. — Proboscis shorter than body. Tentacles 

 lingered. 



Genus. Sipcnculus.— Proboscis long as body. Tentacles 

 not fingered. 



Genus. PentaCTA (includes CccumariaV — Suckers alternate 

 in each row, close. Tooth-plates nearly square. Tentacles ten. 



Genus. Psolinus. — Body curved. Suckers distinct from 

 each other. Under suckers bent. Teeth short. Tentacles ten. 



Family. SYNAFTAD.E.— Suckers none. 



Genus. SyXapta. — Body cylindrical, slender, long. Tenta- 

 cles long, and fingered at tips. 



Order. HOLOTH U ROI DEA.— Shell none. Skin with chalky 

 netted piece-.; a ring of same substance round gullet Loco- 

 motion mostly by suckers. 



Family. PSOLIDiE. — Suckers three rows an oblong disc; two 

 rows rudimentary. 



Gfinus. Psolus. — Body irregular, slug-like. Tentacles ten. 



Family. PENTACTAD.E,— Suckers in five regular rows. Body 

 irregular. 



Order. ECHI NOIDEA.— Shell chalky, either spherical or 

 disc-like, formed of immoveable plates. Locomotion by spines 

 and suckers. 



Family. CIDARIDJE — Body globular. Mouth above and 

 vent below, in centre of body. Five unbroken avenues. 

 Teeth complicated. 



Genus. Echinus. — Spines of same form, the knobs of shell 

 not perforated. 



Genus. Cidaris. — Spines of several forms; knobs of shell 

 perforated. 



Genus. SPATANGIDJE.— Mouth below, not in centre. Vent 

 at one side. Avenues not continuous. Teeth wanting. 



Genus. Spatamiis. — Body heart-shaped, flattened. Ave- 

 nues above and below. No dorsal impression. 



Genus. Amphidotcs. — Body heart-shaped, convex. An im- 

 pression in four of the dorsal avenues. 



Genus. Biiisst's. — Body heart-shaped, convex, dorsal impres- 

 sion enclosing avenues. 



Family. CLYPEASTERIDS;.— Mouth and vent both below; 

 mouth in centre, toothed. Avenues not continuous. 



Genus. Echinarachxiis. — Body nearly circular, very flat, 

 edge nearly entire. Avenues short. Vent between mouth and 

 hinder edge. 



Genus. Encope. — Body flat, nearly circular, lobed and 

 pierced with keylike-shaped holes. South America. 



Genus. Rotdla. — Body flat, front of disc cut into deep teeth; 

 hinder edge not lobed, nearly entire. South America. 



Sub-class, HYPOSTOMATA.— Stomach sac-like, only one 

 aperture. Body lobed or raved. 



Order. ASTEROIDEA. — Shell composed of many moveable 

 pieces. Skin sometimes leathery, sometimes calcareous. Di- 

 gestive canal symmetrical. 



Family. ASTERIAD.E.— Kays developed from body. Loco- 

 motion by suckers under rays. 



Genus. Asterias. — Body star-shaped. Bays flattish and 

 short, edged with plates. Avenues edged with three sets of 

 spines, two rows of suckers in each avenue. 



',tims. Uraster. — Body rather conical, rays rounded, two 

 rows of suckers in each avenue, and three sets of spines. 



Genus. Goxiastkr. — Body conical, edged with spiny plates. 

 Avenues edged with cross rows of spines. 



Genus. Asterin.e. — Body covered with short spines on both 

 surfaces. Avenues edged with a single row of spines. 



Genus. Pai.mipes.— Body flat, thin, with small tufts of spines. 

 Avenues edged by longitudinal tufts of spines. 



Hemes. Solaster. — Many rays, covered with tufts of spines. 

 Avenues edged with three sets of spines, and furnished with two 

 rows of suckers. 



Genus. Cribella. — Rays few, covered with spiny tubercles. 

 Avenues edged with two sets of spines. 



Family. OPHIURIDJE. — Kay.- long, affixed to round disc like 

 the body of an Echinois. Locomotion by suckers. 



Sub-family. Optuurina. -Kays -iniple. 



Genus. Grimms. — Rays scaly, prolonged at disc. Large 

 shield-like plates at origin. Threads between spines simple. 



Genus. OphioCoMA.— Rays scaly, not prolonged at disc. 

 Small pentagonal plates at origin. Threads between spines 

 pinnate. 



