COMPOSITION AND ORIGIN. 201 
indicated in the list by asterisks. All are wide-ranging East Indian and Pacific 
species and are not in any particular (except apparent absence from the Murray 
Island region) separable from the other 69 species. 
Lisr 5.—Species of the Barrier Reef Arca. 
Comatella maculata. Ophiacantha discoidea. Echinothrix calamaris. 
stelligera. Ophiothrix demessa. Echinothrix diadema. 
Comanthus alternans. propinqua. Stomopneustes variolaris. 
bennetti.* trilineata. Echinostrephus molare. 
luteofusca. Ophiothrix virgata. Parasalenia gratiosa. 
samoana. Ophionereis porrecta. Heterocentrotus mamillatus. 
schlegelii. Ophiocoma brevipes Metalia sternalis.* 
Stephanometra monacantha. var. variegata. | Brissus latecarinatus. 
Lamprometra brachypecha. erinaceus. Maretia ovata.* 
te ee A pica. Polyplectana kefersteinii. 
stropecten polyacanthus. schcenleinii. Synapta maculata. 
Culcita noveguineer. ; a ret ate 
Rego ropecanniieca: ; scolopendrina. Chiridota rigida. z 
ee iad anillerso alley Ophiomastix annulosa. Phyllophorus schmeltzii. 
Narion mollis, asperula, Pseudocucumis aciculus. 
eo ed oni: caryophyllata. Labidodemas semperianum. 
pauciforis. flaccida. Holothuria arenicola. 
Linckia leevigata. mixta. GUN ZUSE 
Leiaster speciosus. Ophiarthrum pictum. edulis. 
Ophidiaster granifer. Ophiarachna incrassata. immobilis. 
squameus. Ophiarachnella gorgonia. marmorata. 
Asterina burtonii. septemspinosa. pervicax. 
exigua. Ophioplocus imbricatus. rugosa. 
Acanthaster planci. Phyllacanthus imperialis. Thelenota ananas. 
Ophiacantha confusa. Centrechinus savignyi. Actinopyga nobilis. 
Since this Barrier Reef group is so wholly absent from the Thursday Island 
region, the question naturally arises whether there is a group of East Indian species 
occurring in that region and absent (as a rule) from Mer. List 6, of 33 forms, 
shows that there is such a Thursday Island group, and its composition is of 
considerable interest. 
List 6.—Species of the Thursday Island Area. 
Comatella nigra.* Centrechinus setosus.* Peronella lesueuri. 
Luidia forficifera. Astropyga radiata. orbicularis. 
Ogmaster capella. Lytechinus verruculatus. Fibularia volva. 
Euryale aspera. Temnopleurus toreumaticus. Echinodiscus tenuissimus. 
Amphiocnida dilatata.* Salmacis belli. Schizaster lacunosus. 
Ophiothrix nereidina.* dussumieri. Lovenia elongata. 
Ophionereis semoni. virgulata. Opheodesoma glabra. 
Pectinura arenosa. Temnotrema sculpta.* grisea.* 
Ophiochasma stellatum. Arachnoides placenta. Holothuria coluber.* 
Ophiura kinbergi.* Laganum depressum. scabra. 
Ophiolepis cincta.* laganum. Actinopyga lecanora.* 
This group is not so sharply defined as is the Barrier Reef group, and it includes 
a number of species which might perhaps with equal justice go in one of the other 
lists. There are 10 species that occur at Mer (indicated by asterisks), but like the 
Murray Island species in list 4 they seem to have reached that region from the 
west, not from the east. It is true that Ophiolepis cincta and Centrechinus setosus 
occur in the Pacific, but neither is known from the New Guinea-New Caledonia 
region, while they do occur in the region northwest from Torres Strait. There are 
10 species in list 6 which are not yet actually known from the Thursday Island 
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