A. H. CLARK : THE CRINOIDS OF THE INDIAN OCEAN. 21 



Zygometridce. 



The family Zygometiidse has a singularly restricted habitat, all the species 

 being confined within an area delimited by the northern Australian coast, the 

 Andaman Islands, and the Mergui Archipelago, the Philippine Islands, Hong 

 Kong, and southern Japan. Like the Comasterinse it is not represented in the 

 Atlantic, but many species, representing all the three genera, occur as fossils in 

 the later horizons of Europe. I have already (suggested that the genera of this 

 family and those of the Coraasterinse , which occur fossil in Europe, as well as the 

 recent genus Leptoittetra which evidently was derived from Psathyrometra through 

 such species as Ps. gracillima and Ps. mira, and Antedon, probably reached 

 Europe by passage "overland ' ' north of what is now India. 



Of the three genera of the family inhabiting the recent seas, Catoptonietra 

 has the most restricted range, occurring only from the Philippine Islands to 

 Japan. Eudiocrinus inhabits the same area, but extends also to the Moluccas 

 and the Andaman Islands. Zygometra is more southern, occurring abundantly 

 on the northern coast of Australia, and thence northward to the Mergui Archi- 

 pelago, Singapore, Hong Kong and the Philippine Islands, its distribution closely 

 parallehng that of Comatula Solaris and C. pectinata. 



All of the species composing this familj' are primarily inhabitants of shallow 

 water; only three of them, all belonging to the genus Gatoptoinetra, and' all 

 occurring in, and peculiar to, southern Japan pass the 60-fathom line, and the 

 greatest depth is only 153 fathoms (C. hartlaubi). 



HimerornetridcB. 



As we found to be the case with the Comasterinse and the Zygometrid;e . all 

 of the species of the Himerometridae are confined to the East Indian region. The 

 distribution of the family very closely resembles that of the Comasterinse, and as 

 a whole it covers exactly the same area, occurring from the east coast of Afi'ica to 

 northern Australia and Japan. All of the species are littoral, none extending 

 deeper than 50 fathoms. Of the 38 species 23, or about two-thirds, are confined 

 to the region limited by the northern coast of Australia, the Andaman Islands, 

 Smgapore, the Philippine Islands, and New Guinea. This number includes almost 

 all of the ten-armed species, and also nearly all of those with a very great number 

 .of arms, each type being an equally great deviation from the family mean, or the 

 average for the family. Outside of this area the species are of medium size and 

 have about twenty-five arms. 



The genus Amphimetra is found throughout the range of the family, from 

 east Africa to Japan, Craspedometra and Heterometra occur from east Africa to 

 northern Australia, Hong Kong, and the Philippine Islands , while Himerometra 

 is known from the region between the Persian Gulf and the Philippine Islands,, 

 not being found in Australia ; a single species, H. persica, covers the entire range 

 inhabited by the other seven species of the genus, besides extending further to 

 the westward than any of them. 



