ECHIXOTHUPvID^. 



147 



TABLE OF THE MORPHOLOGICAL CHARACTERS OF THE ECHINOTHURID^ 



AND DIADEMATIDiE. 



Structure of 

 Ambulacra. 



InTERAMBUIjACRAL 



Areas. 



Primary Tubercles. 

 Abactinal System. 



ACTINOSTOME. 



Teeth. 

 Jaws. 



Perignathic 



Girdle. 

 Arrangement op 



Tube-feet. 



Spines. 



Stewart's Organs. 



Gills. 

 Alimentary Canal. 



Pedicellari^e. 

 Globiferous. 

 Opliicephalous. 



Triphyllous 



Tridentate. 



Tube-feet. 



Sph^ridia. 



Calcareous 

 Spicules. 



Color. 



Size. 



DlADEMATID^. 



Diadematoid ; each compound plate 

 consists of a middle primary, and 

 abactinal and actinal secondary ele- 

 ments. Adoral imbrication usually 

 slight or wanting. 



Interambulacral plates bevelled on 

 edge. 



Primordial interambulacral plate re- 

 sorbed. Aboral imbrication not 

 usually noticeable. Without evi- 

 dent membranous interspaces. 



Perforated; usually crenulated. 



Large; anal system covered by nu- 

 merous small plates ; anal tube often 

 present; commonly 2-5 oculars in 

 contact with anal system; genito- 

 ocular ring continuous, with rare ex- 

 ceptions ; genital plates seldom split. 



With five pairs of buccal plates and 

 more or less numerous small scat- 

 tered plates, either confined to, or 

 much more conspicuous in the am- 

 bulacral areas. 



Grooved. 



More or less erect, with open foramen 

 magnum. 



Continuous; auricles and apophyses 

 more or less extensively developed. 



In three longitudinal series, com 

 monly; sometimes in two; rarely 

 in one actinally. 



Hollow; long, usually verticillate 

 sometimes smooth; hoofs and con- 

 spicuous skin-sheaths wanting. 



Rudimentary or usually wanting. 



Well-developed. 

 Long and large; oesophagus long and 

 more or less coiled. 



Wanting (except Centrostephanus). 

 Valves constricted at middle; blade 



deeply hollowed, with little calca 



reous material within. 

 Flat and leaf-sliaped, commonly with 



out cover-plate. 

 Very diverse, both large and small. 

 With sucking disc actinally, but usually 



not abactinally. 

 Usually numerous, not sunken in pits, 



arranged in a vertical series, at inner 



side of inner series of tube-feet, in 



each half amtulacrum. 

 Essentially triradiate, often forming 



perforated plates. 



Usually very dark, black, olive, purple, 

 or red ; sometimes light ; spines often 

 banded. 



Usually large, up to 150 mm. h. d. 



ECHINOTHURID^. 



Essentially diadematoid; some di- 

 versity shown in relative size and 

 position of plate-elements. Adoral 

 imbrication usually well-marked. 



Interambulacral plates imbricating. 



Primordial interambulacral plate re- 

 tained. Aboral imbrication more or 

 less marked. Membranous inter- 

 spaces often very marked. 



Perforated; non-crenulated. 



Large; anal system covered by nu- 

 merous small plates; anal tube 

 wanting; all oculars in contact with 

 anal system; genito-ocular ring 

 often discontinuous; genital plates 

 often split. 



Covered by five double columns of 

 perforated ambulacral plates. 



Grooved. 



More or less inclined, with open fora- 

 men magnum. 



Continuous; auricles and apophyses 

 more or less extensively developed. 



In one, two, or three longitudinal 

 series. 



Hollow; short, usually smooth and 

 very rarely verticillate, hoofs or 

 conspicuous skin-sheaths often pres- 

 ent, at least on actinal primaries. 



Well-developed ; rarely rudimentary, 

 and possibly wanting :n some in- 

 dividuals. 



Commonly well-developed. 



Long and large; oesophagus long and 

 more or less coiled. 



Wanting. 



Valves very wide near tip and deeply 



constricted, essentially as in Dia- 



dematidiB. 

 Flattened and widened at tip, with 



cover-plate. 

 Very diverse, both large and small. 

 No sucking disc abactinally, and often 



not actinally. 

 As in Diadematidse. 



Usually perforated plates, often show- 

 ing triradiate origin; sometimes tri- 

 radiate spicules. 



Deep purple, red, dull yellowish, gray, 

 or greenish; spines often banded. 



Large, 70-320 mm. h. d. 



