EEPORT ON THE ASTEROIDEA. 325 



armature consists of a marginal series of abou t eight short, lamelliform spiuelets, similar to, 

 but larger than, those on the adambulacral plates, which increase in size as they proceed 

 inward. On the actinal surface of each mouth-plate, near the inner end, is one spine- 

 let, exactly similar in size and shape to the corresponding spinelets on the adambulacral 

 plates. 



The actinal interradial areas are large and occupied by intermediate plates which are com- 

 paratively large in size and few in number. All are slightly tumid and covered with the 

 uniform granulation and membrane already referred to. Each of the plates in the series 

 next the adambulacral plates bears a number of small, two-lipped, valvate pedicellarise, 

 similar to those in Anthenea, but uniform in height with the granulation; from three to 

 seven are present on a plate and show no definite order of arrangement. A few of the 

 other intermediate plates bear occasionally a similar but isolated pedicellaria. Not more 

 than three series of intermediate plates, and perhaps a few supplementary ones, are 

 present. 



The madreporiform body, which is large and elongately oval, is situated external to 

 the basal plate. It is bounded laterally and outwardly by two large plates ; and its outer 

 end is rather nearer the centre than midway between that point and the margin. Its 

 surface is marked with very fine striations, which radiate with more than usual regularity 

 from the centre to the margin. 



The ambulacral tube-feet are large and have very large fiat sucker-disks. 



The primary apical plates are easily distinguishable on the disk : — The dorso-central, 

 the under-basals, and the basals, the last mentioned being especially conspicuous. When 

 the madreporiform body is placed in the right anterior interradium the anal aperture is on 

 the right posterior side of the dorso-central plate. 



Small, isolated, pincer-formed pedicellariae, with two rather coarse jaws, are present 

 here and there on the abactinal plates, and occasionally on the infero-marginal plates in the 

 interbrachial arcs near the lateral spines. 



Colour in alcohol, a bleached yellowish white. 



Young Phase. — The smallest example collected by the Challenger which measures 

 R = 85 mm., r = 25 mm., has only two lateral spines on each infero-marginal plate, and 

 the longest of these measures about 7 mm. This specimen has twenty supero-marginal 

 plates, and in all other essential respects corresponds to the description given above. 



Locality. — Station 187. Booby Island, Torres Strait. September 9, 1874. Lat. 

 10° 36' 0" S, long. 141° 55' 0" E. Depth 6 fathoms. Coral mud. Surface temperature 

 77°'7 Fahr. 



Remarks. — This species is readily distinguished from all other species of Stellaster by 

 the three large lateral spines, by the tumid marginal plates, by the character of the 

 armature of the adambulacral plates, as well as that of the actinal intermediate plates. 

 The character of the abactinal plates points to its close affinity with Goniodiscus. 



