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

;ECHINODEKMATA. 16314. Antedon briareus. (Plate XIV,)Centrodorsal flattened ;15-20 marginal delicate cirri, formed ofa few short joints.Arms more than 70.First radials obscured ; second in contact, at least three times aslong as they are broad ; third widely triangular. Three distichals,the axillary a syzygy ; two palmars. If there is another divisionthere are again two joints ; no syzygy. The first five or six brachialshave nearly even edges ; the succeeding ones are markedly wedgeshaped.A syzygy on the third brachial ; succeeding syzygies rare.Second pinnules longer than first, very delicate, made up of anumber of small joints ; the succeeding pinnules stouter and morefleshy.This is one of the species in which there is a very considerabledifference in the length of the arms ;here some of the arms may beas much as 110 millim. long, while others are only 75 millim.There is an interradial plating, extending as far as the distichalaxillary.The colour (in spirit) is dark brown.Port Denison.15. Antedon microdiscus. (Plate XV.)Centrodorsal rather large a»d prominent ; the cirri marginal, intwo or three rows, from 30-50 in number, with from 50-70 joints,none of which are markedly longer than broad ; as a rule, the distaltwo thirds have an inconspicuous dorsal spine, and in the largerspecimen the penultimate spine is hardly more conspicuous.The first radials visible ; all very short and wide, the second notin contact. Three distichals, the axillary a syzygy. Three palmars,the axillary normally a syzj-gy. The arms may divide again, and ofthe three joints the axillary may or may not be a syzygy. Probablyas many as 90 arms in an adult. The earlier brachials have fairlyeven edges, are well rounded above and fiattened at their sides ; thenext succeeding are faintly wedge-shaped, the distal edge of eachprojecting alternately on either side into a slight protuberancefurther out, the wedge-form disappears. The arms generally, thoughslender, are very firm and stiff and are set verj' close to one another.Syzygies 3, 22-25, 40-41; then from 10-12 joints betweeneach.The earlier pinnules exceedingly long in the adult, with verystout slightly keeled basal joints ; the second, which is a good deallonger than the first, has as many as 50 joints and is qiiite fine atits free end ;the more distal joints are provided with a spine or tuftof spines.The stiff straight arms are about 150 millim. long; the cirrimeasure nearly 50 millim. ; the disk, with rounded incisions, has adiameter of about 12 millim.The disk and the arms, as far as their last division, are largelym2