COMPOSITION AND ORIGIN. 199 
land coast of Australia or in the Thursday Island region unless it also occurs at the 
Murray Islands. The significance of this fact will be referred to subsequently, in 
connection with the interpretation of all the data. 
List 2.—Species of very wide range. 
Comanthus annulata.* Toxopneustes pileolus.t Holothuria atra.* 
parvicirra.* Mespilia globulus.+ cinerascens. ¢ 
Lamprometra protecta.t Echinometra mathzi.* difficilis. ¢ 
Fromia monilis.f Heterocentrotus trigonarius. t greffei.t 
Linckia multifora.f Echinoneus cyclostomus.* impatiens.* 
Tamaria pusilla. Oligopodia epigonus.f leucospilota.* 
Echinaster luzonicus.* Metalia spatagus. ft monocaria.* 
Mithrodia clavigera.f Brissopsis luzonica.t pardalis.* 
Amphipholis squamata.* Lovenia subearinata.f tenuissima. ft 
Ophiactis savignyi.* Opheodesoma serpentina.t vitiensis.t 
Ophiothrix longipeda.* Synaptula reticulata. Stichopus chloronotus.* 
purpurea. f Leptosynapta oéplax.t Actinopyga mauritiana.* 
Eucidaris metularia.t Polycheira rufescens.f 
Still a third group, whose value in distributional study is small, is made up of 
species which are known from more than one place, generally from two or more 
widely separated areas, but which are of such rarity or of such indefinite and uncer- 
tain range that we lack the data for determining even their approximate distribu- 
tion. A few species are also included here which have an extended range outside 
the area under discussion, but are only known from a single isolated record within 
it. Altogether there seem to be 29 species which must be placed here. (See list 3.) 
List 3.—Species of imperfectly known range. 
Heterometra nematodon. Ophiactis luteomaculata.* Synaptula nigra. 
Colobometra perspinosa. modesta. Protankyra similis. 
Astropecten granulatus. Ophiomaza obscura. Cucumaria semperi. 
Archaster angulatus. Ophionereis dubia. Pentacta challengeri. 
Goniodiscaster coppingeri. Ophiocoma wendtii. cucumis. 
pleyadella. Ophiarachnella megaloplax. Actinocucumis difficilis. 
Linckia guildingii. Prionocidaris verticillata. Holothuria hypamma. 
Retaster insignis. Clypeaster humilis. remollescens 
Amphiodia mesopoma.* Echinocyamus crispus. Actinopyga parvula. 
Amphioplus relictus. Synaptula indivisa. 
This is really a very heterogeneous list. Only 5 occurred at Mer, and of the 
other 24 I have seen but 3 in life. Several of the species are of doubtful authenticity, 
and some of the records are based on young or imperfect specimens, the identifica- 
tion of which is open to doubt. All in all, this list is the least useful or significant 
of any of those into which the tabulated list is subdivided. The two species 
marked with an asterisk are among the forms mentioned as having a possible 
southern affiliation. 
There remain, then, 181 forms concerning the range of which we have sufficient 
knowledge to justify us in undertaking to group them according to their distribu- 
tion. Of these, about one-third appear to occur along the whole northern coast 
of Australia, or at any rate are known from the eastern coast of northern Queensland 
as well as from the coast of northern West Australia. There is a possibility that the 
Gulf of Carpentaria is really ‘‘an impassable gulf’’ and that no species of echino- 
derm ranges along the entire northern coast of the continent with even approximate 
continuity; but since there is no good reason for believing this to be the case, I 
