A, H. CLARK : THE CRINOIDS OF THE INDIAIf OCEAN. 9 



Owing to the existence of many and varied barriers to the dispersal of the 

 littoral individuals we may confidently assume that when we find a family, 

 genus, or species widely spread along the shores that that species, genus or 

 family, has a considerable bathymetric range, and the reverse. For instance the 

 entire genus Zygometra is known only from an area delimited by the northern 

 coast of Australia, the Mergui Archipelago, Singapore, Hong Kong, and the 

 Philippine Islands. We may assume, therefore, that it is confined to the littoral 

 belt, and the facts, so far as they are known, bear us out. Moreover, as it 

 occurs in the Jura of Europe as a fossil, we may assume a past littoral connec- 

 tion between Europe and the East Indies. Upon finding an Isocrinus in the 

 West Indies m 5 fathoms and a Metacrinus in Japan in 60, we would assume 

 that the Pentacrinitidse are able to live in deep water, and here again the 

 known facts accord with the deductions. This rule, of course, does not hold 

 good for animals capable of dissemination as pelagic larvae or eggs. 



The East Indian faunal region or, as I have called it, the Indo-Pacific- 

 Japanese, includes the east coast of Africa from Suez to the Cape, and extends 

 thence eastward, embracing the southern shores of Asia, all the shores of Australia 

 and Tasmania (but not New Zealand), reaching the Tonga Islands, Fiji, Samoa, 

 the Caroline Islands, the Philippines, and, to the northward, southern Japan and 

 the Korean Straits. The conditions within this region are far from being uniform. 

 With an area of maximum intensity within a triangle whose apices are Luzon, 

 Borneo, and New Guinea in which 18 of the 19 families (all but the Phrynocrinidae) 

 and 71 of the 82 genera (all except Cominia, Ptilomeira, Mastigomeira , Erythro- 

 metra, Zenometra, Comastrocrinus , Carpenterocrinus ^ Calamocrinus, Ptilocrinus, 

 Hyocrimis, and Phrynocrinus) are known to occur, the fauna extends southward 

 about Australia, becoming modified on the northern coast by a great reduction m 

 the number of species (only about one-eighth of the total number occurring here), 

 the absence of nine families, and four of the five subfamilies of Antedonidae 

 'Stephanometridae, Pontiometridae, Calometridae, Perometrinse, Zenometrina?, 

 Heliometrinse, Thysanometrinae, Atelecrinitidae, and all the stalked families 

 except the Pentacrinitidae) , and the absence of 19 genera, {Comissia, Cominia, 

 Eudiocrinus, Catoptometra, Himeromelra , Selenemetra, Mariametra, Cyllometra, 

 Pterometra, Stenometra , Parametra, Glyptometra, GMorometra, Poecilometra, Stro- 

 tometra Gharitometra , Mastigometra, Iridomelra, and Toxometra) ; this loss 

 is partly compensated by additional species in the genera Gomatula, Zygo- 

 metra Comaster, Heterometra, and Dichrometra , while these, together with dis- 

 tinctive local species, characterized by curiously exaggerated peculiarities of 

 structure supplanting the common East Indian forms, in Gomanthina and Oligo- 

 metra, give to the fauna a definite facies; to the southward attenuation and 

 specialisation increase until on the southern coast we find only seven species, all 

 peculiar to the region, furnished by five genera, of which two are confined to this 

 district (Comatulella ; Ptilometra) ; these seven species are, ComatuleUa brachiolata, 

 Comanthus trichoptera, OUgometra thetidis, Ptilometra macronema, Pt. miilleri, 



