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Show 1900.] MR. F. P. BEDFORD ON MALAYAN ECHINODERMS. 279 unrepresented in the peristome of Echinothuridce), number in adults normally 9 in one row and 8 in the other row of the pair, although occasionally there may be 8 and 7 respectively. In A. urens there are 9 in each row (according to the Sarasins), and in A. grubei there are 12. The coronal plates, both ambulacral and interambulacral, are like those described by M . de Loriol for Amboina specimens of A. varium, but the ambulacral edge of the narrow interambulacral plates is devoid of tubercles. There are three distinct kinds of pedicellariae. Stewart's organs are very well-developed and of the same shape as in A. urens, and the muscular partitions are developed to the same extent as in that form. The alimentary canal does not seem to have been described in detail in any species of the genus, so that I do not know if the condition occurring in this species in universal throughout the genus, or whether it forms a " specific character " ; but in addition to the two loops of the alimentary canal occurring in other regular Echinoids (the adoral of the two being connected with the siphon), it makes two additional loops within the former before reaching the " siphonal intestinal loop," these additional loops being situated round the top of the lantern of Aristotle (the siphon appears to be absent). r.s. w.v b.v. en. o.r.n c.p. c.t '&%£.<*&& .^iJ&tJiiy&nb - 'y -' kl N / Radius of Asthenosoma heteractis (transverse section). This section passes between the branches to the ambulacral pores, and is thus slightly oblique. w.v. - radial water-vessel. b.v. - radial blood-vessel ? r.s. = radial sinus (pseudohaemal canal). s. = septum between outer and inner radial nerves. e.n. = epineural canal. ms. = mesentery formed from the endothelium of the body-wall. c.e. = endothelium lining body-wall. c.p. == calcareous plate (decalcified). c.t. = connective tissue. i.r.n. = inner radial nerve (ganglion). o.r.n.= outer radial nerve. Another character of some morphological interest which does not seem to have been noticed by the Drs. Sarasin in A. urens, or 19* |