KEPOET ON THE ASTEROIDEA. 381 



Disk large, convex, and much inflated. Rays elongate, narrow, and more or less 

 rounded cylindrically. Margin rather angular, the marginal plates being very incon- 

 spicuous. Interbrachial arcs wide and rounded. Actinal surface concave and deeply 

 depressed within the disk (possibly this is either a mere body contraction, or may 

 indicate the formation of a nursing cavity such as occurs in some forms of Asterias and 

 Echinaster). The actinal surface of the rays is slightly convex. 



The abactinal area is covered with small irregularly disposed plates, which bear 

 groups of from three to ten spinelets. The spinelets are short, subequal, papilliform, 

 covered with membrane and imbedded at the base in a thick fleshy mass, the groups 

 looking more like irregular echinulated masses than paxillae. The form of the masses 

 varies considerably, and elongate groups are not infrequent. Large and smaller groups 

 are interspersed irregularly, and all are widely spaced. In the interspaces are numerous 

 large papulae, and groups of three to five may be counted. 



The marginal plates, which are very small and quite inconspicuous, are at first sight 

 scarcely distinguishable from the actinal and abactinal plates on the median part of the 

 ray, and much irregularity occurs in their size. In the interbrachial arc and on the 

 outer half of the ray they are more distinct ; and the superior and inferior series are 

 seen to alternate to a certain degree. The plates, which are subequal and similar in 

 character, are covered with small papilliform granules, skin-covered and imbedded in 

 membrane similar to those on the abactinal and actinal plates. More than fifty iufero- 

 marginal plates may be counted between the median interradial line and the extremity, 

 but it is scarcely possible without dissection and preparation to count the number 

 accurately on account of their small size and the interference of intermediate plates on 

 the middle part of the ray. 



The adambulacral plates are short, and their armature consists of: — (I.) A single large 

 spine on the furrow margin, which is very robust and cylindrical at the base, but flattened 

 and truncate at the tip like a chisel in the direction transverse to the axis of the ray. 

 These spines are thickly covered with membrane. On the ten or twelve plates near the 

 mouth there are two spines on the furrow margin, very obliquely placed, the adoral one of 

 the pair being pushed far back. (2.) On the actinal surface of the plates is a lineal series 

 of three short, subequal, skin-covered, papilliform spinelets, much smaller than the furrow 

 series, slightly tapering at the end but obtuse, the direction of the series being usually in a 

 straight fine behind the furrow spine, at right angles to the furrow, but sometimes slightly 

 oblique. Occasionally there is a fourth spine in this series, and sometimes the line of the 

 series is slightly curved. 



The actinal intermediate plates are small and form well-defined longitudinal series, 

 two of which extend nearly to the end of the ray : about eight series may be counted on 

 each side of the median interradial line. Each plate bears a group of from three to seven 

 short, subequal, slightly tapering spinelets, covered with skin and imbedded at the base 



