Report on the zoological collections made in the Indo-Pacific Ocean ...

ECHIJfODEEMATA. 137plates are curved ; the plates themselves are at first broader thanlong, but during their gradual diminution in size they have at onetime their aboral edge equal to their longitudinal axis ; still furtherout they are longer than broad. About six, short, poorly developedspines are found on each of the side arm-plates near the disk, ofwhich the largest are median in position ; they diminish in numberand size as they approach the free end of the arm. Two small tentacle-scales.Upper surface (in alcohol) dark yellow, with spots or patches ofbrown ; the whole of the actinal surface pale flesh-colour. Although,as a rule, three consecutive segments are coloured by a darker transversepatch, there may be only two, or there may be four so ornamented,and, as irregularities, one or more than four ; but the colorationalways extends on to the sides of the arm, though it neverpasses on to the lower surface. Or the whole may be very manyshades darker, and then the darkest parts are not especially remarkable; this last mode of coloration appears to be by far the mostcomnion.Port Molle, Queensland, 14 fms., rock ; and Port Denison,3-4 fms.In some examples, which are very much smaller, from Torres Straitsthe radial shields are oviform, the upper arm-plates are not nearlyso wide nor so distinctly carinated ; the central rosette may be onlybarely indicated, though the central plate is very distinct ; the platesof the interradial series have no small marginal secondary plates.The side arm-plates at the base of the arm are proportionately muchlarger, and in consequence diminish the breadth of the lower as wellas of the upper arm-plates. Striking as is the difference in effectproduced by these dift'erences in character, they are, I think, onlyto be ascribed to age.5. OpMopeza conjimgens.This species seems to strengthen the opinion, more than once expressedby Mr. Lyman, that the genera O/ihiojJeza and Pectinura arebarely to be distinguished. AVithout a divided mouth-shield, it hasthe arms not rounded, as in 0. fallcuv, but keeled above, as is so oftenthe case in Pectinura.Most closely allied to 0. fallax, it may be distinguished by thesomewhat coarser granulation of its disk, the smaller number ofmouth-papillse, and the broadened upper arm-plates.Disk pentagonal, flattened, 17'5 millim. diam. in one example,completely covered by a delicate and regular granulation (of abouttwenty granules to 1 millim.), the underlying scales not large ; theradial shields, in perfect specimens, only indicated by depressions.Mouth-shields not divided, wider than long, with a wide convexadoral edge, straighter sides, and a barely convex aboral margin.Side mouth-shields small ; the space between the mouth-shield andthe edge of the jaws is marked by a granulation, much coarser thanthat which obtains elsewhere on the disk. Mouth-papillae seven.