EEPORT ON THE ASTEROIDEA. 50 1 



The outer extremities of the actiuo-lateral spines are not pointed, but rounded ; and the 

 web tissue is scarcely indented. Owing to the abnormal growth both of spine.-; and 

 tissues in the interbrachial arc, and the tension produced thereby, the majority of the 

 spines at the extremity of the ray are made to radiate inward towards the angle, and the 

 web appears considerably stretched. 



Colour in alcohol, yellowish grey. 



Locality. — Station 325. Off the coast of South America, east of Buenos Ayres; 

 March 2, 187G. Lat. 36° 44' 0" S., long. 46° 1G' 0" W. Depth 2650 fathoms. Blue 

 mud. Bottom temperature 32° - 7 Fahr. ; surface temperature 70° "8 Fahr. 



Remarks. — This species is characterised by the peculiar parchment-like appearance of 

 the supradorsal membrane ; and may be recognised by the presence of only a single spine 

 in the adambulacral armature and by having very small spiracula, which are arranged in 

 groups and irregularly distributed. 



4. Hymenaster sacculatus, Sladen (PI. LXXXV. figs. 1-3 ; PI. LXXXVI. figs. 7-9). 

 Hymenaster sacculatus, Sladen, 1882, Journ. Linn. Soc. Lond. (ZooL), vol. xvi. p. 217. 



Marginal contour stellato-pentagonoid ; interbrachial indentations small ; rays usually 

 recurved abactinally, making the abactinal area deeply concave, the actinal being convex. 

 Minor radial proportion 66 - 6 per cent. B = 42 mm. ; r = 28 mm. Pays tapering 

 somewhat sharply at the extremities ; marginal fringe distinct and well developed. 



The supradorsal membrane is thick and coriaceous in appearance. The papillae are 

 numerous, and have crowns with rarely more than four or five spinelets, which are promi- 

 nently protrusive of the membrane — that portion lying between the tips of each individual 

 crown being thick, devoid of spiracula, and forming a slightly distended saccular area. 

 Thick bands of tissue, with fibres, radiate between the crowns, and the narrow interspaces 

 are occupied by numerous small spiracula, generally three or four, or even more, in line 

 together, separated only by very fine, thin dissepiments. The oscular orifice is large ; 

 the valves, five in number, are regular, and form when closed a compact exactly fitted 

 pyramid, which rises as a small cone in the centre of the concave abactinal area. The 

 spinelets of the valves are of moderate length, thickly webbed, and with numerous 

 spiracula in the interspaces. 



The ambulacra! furrows are moderately wide and very uniform in breadth, except 

 towards the extremity, where the}* taper rapidly, and near the mouth, where they are 

 also somewhat constricted. The armature of the adambulacral plates consists of two 

 spines of moderate length, but with a very long sacculate investing membrane, the pairs 

 standing slightly oblicpie to the median line of the ray. The aperture-papillae are large, 

 thickly invested, subspatulate, and slightly constricted near the outer third. 



The mouth-plates are elongate, largely keeled, prominent aborally, and each plate 



