OCR Text |
Show 86 PROF. F. J. BKLL ON THE [Feb. 19, the dorsal ossicles is very well marked ; three rows of pore-areae extend along the greater part of each side of the arm. Madreporic body rather obscure, small, irregularly oval, surrounded by an impressed line. Granules cover all the plates, are small and regular, save on the ventral plates, where they are larger and more irregular. Colour (in alcohol) yellowish white. R = 1 4 0 millim.; r = 4 7 millim. Hab. Billiton. I have dedicated this species to the memory of the late Professor Troschel, who, with Johannes Miiller, was the author of the ' System der Asteriden.' OREASTER MUELLERI, sp. nov. A triplacanthid form allied to O. orientalis, but distinguished from it by the following characters :-There are only two or three, and not as many as five, spines in the second adambulacral row ; nearly all the marginal plates, whether superior or inferior, carry spines; the pedicellariae on the ventral plates are not numerous. R=2*5 r. Disk rather high ; arms rather wide at their base, and stout for all their distance ; spines at the sides half or more than half as high as those of the median row, the apical spines well developed. Spines richly developed on the disk. No spines un the ventral plates. About twenty marginal plates in either series, the lower completely confined to the abactinal aspect, save just at the end of the arm. The superomarginals considerably excavated superiorly, so that their upper edge is triangular; the spines on the upper are more prominent than those on the lower plates, and are developed on nearly all; those on the inferomarginals are occasionally double. There are no pedicellariae on the marginal plates. Adambulacral spines in three rows ; in the innermost eight delicate spines, of which the outer in each set are remarkably small ; each set is separated from its neighbour by a forcipiform pedicellaria; in the middle row two, sometimes three, much stouter spines ; in the outermost row two or three, not quite as stout ; these spines decrease in number on the distal plates. The immediate buccal armature appears to be formed by the elongation of the spines of the lowest row. The ventral plates are best distinguished from one another by the large size of some of the tubercles on each plate ; of these there may be four or more, which may form a rosette. A fairly large number of valvular pedicellariae are developed, especially in the neighbourhood of the ambulacra. The pore-areae are large and numerous, when of a definite form triangular, but at the sides of the arm the reticulation of the skeleton is not as distinct as it is on the disk. Madreporic body irregular in form. Granules unequal, forming a mosaic, never reaching to the tips of the spines. Pedicellariae on the dorsal surface small, forcipiform. Colour (in alcohol) creamy white. R = 9 8 ; r = 3 8 ; breadth of arm at base 34. Hub. Billiton. |