530 *' THETIS " SCIENTIFIC RESULTS. 



tionecl by him, which is so conspicuous he could hardly have 

 overlooked it had it been present in his specimens ; the first 

 fourteen-sixteen large adambulacral spines of the outer series,. 

 beginning at the mouth, are so closely arranged that the distance 

 between two is far less than the diameter of one, while the 

 remainder are widely spaced, the distance between two greatly 

 exceeding the diameter of one ; the transition from the crowded 

 to the open arrangement is abrupt and marked. Should this 

 prove to be a constant character in the Ophidiasters from Lord 

 Howe Island, it would probably entitle them to full specific 

 rank. But it is possible it is only an individual peculiarity of 

 the specimen before me. 



HENRICIA HETERACTIS,io sp. no v. 



(Plate xlix., figs. 1 and 2.) 



Rays 7 (in two smaller specimens 6). R=25 mm., r=8 mm., 

 R^3r. Intei'brachial arcs acute. Rays more or less cylindrical, 

 stout and very blunt. Breadth at base, 7"5 mm. Disc rather 

 large ; vertical diameter, 7 mm. Plates of abactinal skeleton 

 stout and crowded, more or less crescentic, with the concave side 

 towards the centre of the disc. Along the sides of the rays, 

 especially near tip, a more or less distinct, longitudinal arrange- 

 ment can be seen. Papular areas reduced to a minimum, each 

 with a single rather large papula. Spinelets very numerous on all 

 the abactinal plates, minute and very slender; in the interbrachial 

 arcs the spinelets are longer and less crowded. Actinal surface 

 of rays flattened, closely coveted by three or four longitudinal 

 series of squarish plates on either side, each bearing a dense 

 covering of minute spinelets, only a little larger than those of the 

 abactinal surface. Adambulacral armature (PI. xlix., fig. 1) 

 consists of a marginal series of five or six spines, more or less 

 connected by a membrane, the middle one or two about 1mm. 

 long and decidedly longer and stouter than the others; theaboral 

 and adoral ones the smallest. Just outside, and close to this 

 marginal series is another very similar set of four or five spines ; 

 these are a trifle shorter but fully as stout, and are hardly as 

 much united to each other by a membrane. The adambulacral 

 plates are well spaced, and their adoral and aboral margins bear 

 a few small spinelets which may form a continuous series with 

 the outer marginal series. The surface of the plate carries from 

 one to four short, sharp spines. There is no furrow spine. Oral 



^° €Ttpos= other than usual + dKrty=a ray, in reference to the number- 

 of rays. 



