REPORT ON THE ASTEROIDEA. 419 



of supero-marginal plates and the adambulacral plates are five longitudinal and parallel 

 series of plates, the three upper rows forming the sides of the ray and the two lower being 

 on the tumid actiual surface. The plates of the two upper rows of the lateral series are 

 broader than those in the three lower series. The longitudinal arrangement of all the 

 scries is perfectly regular, and the plates diminish gradually in size as they proceed out- 

 ward. Excepting the median radial line, the plates of all the other rows form regular 

 transverse, as well as longitudinal series. The plates of the median radial line are slightly 

 larger than the others and consequently do not correspond. All the plates are contiguous, 

 but leave a small diamond-shaped or subcircular mesh between the rounded corners of 

 adjoining plates. This is covered with membrane, through which one or more small 

 papulae proceed, and on which are usually borne one, or occasionally two, small forficiform 

 pedicellariae. The meshes form perfectly regular longitudinal lines, and this character, as 

 well as their presence, is rendered more conspicuous by the slightly tumid surface of the 

 plates. The surface of all the plates is studded with a number of small, uniform, well- 

 spaced, miliary granules, on which are articulated very short ciliary spinelets thinly 

 covered with membrane. The plates of the median radial series are submammillated, rising 

 to a small but definite tubercle in the middle, which gives attachment to a short, robust, 

 conical spinelet, the surrounding portions of the plate being covered with the same small 

 miliary granules and spinelets as the other plates. The supero-marginal plates are usually 

 similarly mammillated and spined, and in fully grown examples the large interradial plates 

 on the disk and the series of intermediate plates between the median and the supero- 

 marginal series may also bear a spine. The spines on the intermediate series of plates 

 are, however, by no means regular or constant. 



On the plates of the three rows of actinal intermediate plates, which succeed the 

 adambulacral plates, there are usually one to three spinelets much longer and more robust 

 than the accompanying miliary spinelets. These are naked, delicate, cylindrical, and 

 taper to a fine extremity, and are generally arranged in slightly oblique lines, with the 

 middle spine often more forward and longest when three are present, near the lower margin 

 of the plate ; they are also directed upward and appressed to the ray. The next row on 

 the sides of the ray, i.e., the fourth series of actinal intermediate plates from the adam- 

 bulacral plates has one larger spine on each plate of equal size to those just mentioned. 



The adambulacral plates are quite within the furrow, and are short but broad, extend- 

 ing far upward almost vertically. Each alternate plate is developed into a thin prominent 

 ridge, which extends far into the furrow and entirely separates neighbouring tube-feet, 

 whereas the intermediate plates are smooth, and appear to form the true furrow wall. 

 The armature of the prominent adambulacral plates consists of four spines, which are 

 moderately long, cylindrical, and slightly tapering, placed in single file at intervals along 

 the edge of the ridge, the innermost being usually the most delicate, and the outermost 

 usually the shortest. Two to five small forficiform pedicellariae are attached by membrane 



