86 PKOF. 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 im- 

 pressed 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= 140 millim. ; r=47 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 ' Svstem 

 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 

 pedicellarise on the ventral plates are not numerous. 



R=:2".T 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 on the ventral plates. 



About twenty marginal plates in either series, the lower com- 

 pletely 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 jjedicellaria ; in the 

 middle row two, sometimes three, much stouter spines ; in the outer- 

 most row two or three, not quite as stout ; these spines decrease hi 

 number on the distal plates. The immediate buccal armature 

 appears to be formed by the elongation of the spines of the lowest 

 row. The veiitral 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 pedicellarise are developed, especially in the 

 neighbourhood of the ambulacra. 



The pore-arete 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. Pedicellarise on the 

 dorsal surface small, forcipiform. 



Colour (in alcohol) creamy white. 



1{:=!)S ; /•=;:;S ; breadth of arm at base 6A. 



Hah. Billiton. 



