CLARK: EXTENDED RANGE OF GENUS LYDIASTER 143 



alternating rows of seven or eight each, becoming less numerous dis- 

 tally; the granular area is confined to the median portion of the plate, 

 though in the interbrachial arc it may reach the proximal border; in the 

 interbrachial arc nearly all the superomarginals bear near their actinal 

 border a very small deeply sunken spatulate pedicellaria; a narrow 

 border of flattened squarish granules surrounds each superomarginal. 



The inferomarginals are essentially similar to the superomarginal; 

 viewed actinally they are seen to decrease in size from the center of the 

 interbrachial arc to the arm bases, thence much more gradually to the 

 arm tips; in the interbrachial arc in lateral view the inferomarginals 

 are only half as high as the superomarginals (2.5 mm.), but they rapidly 

 increase in height so that on the outer half of the arm the plates of the 

 two series are nearly equal. The inner portion of the inferomarginals is 

 everywhere horizontal, and the inner border is everywhere convex. A 

 border of small squarish granules similar to that on the superomarginals 

 is found on the inferomarginals, and the same granular ornamentation 

 occurs on their surface, though the granules are rather more numerous. 

 In the interbrachial arc the inferomarginals usually carry small exca- 

 vate spatulate pedicellariae just within the upper border, and one or 

 two additional on the ventral (actinal) surface; pedicellariae of both 

 series occur irregularly to the terminal portion of the arms. 



The actinal intermediate areas are extensive; the row of actinal 

 intermediate plates adjacent to the adambulacrals, which extends to the 

 sixteenth superomarginal (the distal third of the arm), is regular and the 

 next row is regular to the arm bases ; a partial third row may be traced, 

 but within the triangular area between this and the inferomarginals the 

 plates, which decrease in size, tend to become arranged in columns 

 perpendicular to the inferomarginals. 



In the center of each of the actinal intermediate plates is a large 

 pedicellaria which resembles those on the adambulacrals, and is more 

 or less proportionate in size to the plate; on the larger plates this is 

 surrounded by several large rounded tubercles, beyond which are the 

 lower tubercles forming the bordering series of the plates ; on the smaller 

 plates only the latter occur. 



The adambulacral plates are oblong, from one-third to one-half 

 again as broad as long, with a very slightry curved furrow margin which 

 is not quite parallel to the groove, the proximal end being slight^ more 

 distant. The furrow series consists of five stout subequal truncated 

 spines, mostly rounded-quadrate in section, the most proximal of which 

 is so situated that it overlaps the most distal of the preceding series. 

 Behind the furrow spines is a series of three or four tubercles, the most 

 distal abruptly the largest, and behind these a long, low, Hippasteria- 

 like bivalved pedicellaria placed somewhat diagonally with its distal end 

 slightly nearer the mid-radial line. Beyond the pedicellaria is a series 

 of two or three large tubercles, and beyond these a series of several 

 smaller tubercles which, with similar tubercles, at right angles to the 

 two ends of this series, delimit the borders of the plate. 



The mouth plates are triangular and inconspicuous, about twice as 



