JAPANESE ASTEIÎOIDEA. 47 



complete enclosure of very small spines around the base of the 

 principal spines, which is more distinct on the arms but much 

 less so or atrophied in the interbrachial angles of the disk. 

 There are besides some very small spines either forming a series 

 near the margin of the plate or more irregularly scattered on its 

 surface. Once in a while, some of the spines near the margin 

 are better developed than usual and together with the similarly 

 developed spines of the next plate form what have been called 

 " pectinate pedicellaria3," which are characteristic of this genus, and 

 appear to have been described so far only from the ventrolateral 

 plates. These structures will be mentioned again later. The 

 lateral margin of the arms is formed more by the inferomarginals 

 than by the superior series. 



Adamhulacrals. — ^The adambulacral plates (PI. I, fig. 4) are 

 nearly twice as broad as long and present each a wedge-shaped 

 surface towards the furrow. At the base of the arms there are 

 two adambulacral plates to each inferomarginal, but further out 

 the adamhulacrals become relatively more numerous, although the 

 ratio of the two may not become as great as three to one. Each 

 adambulacral plate bears at the furrow margin a series of two to 

 three, very lightly curved spines, which may be as long as 

 3.5 mm. at the central end of the furrow. The modal number of 

 these furrow spines is two, but three is not very rare. On the 

 actinal surface of the plate there are 2-4 large spines, forming a 

 single row at right angles to the furrow and making a single 

 transverse series with the inferomarginal spines, where the two 

 sorts of plates happen to coincide. These spines may be as long 

 as 7 or 8 mm., and unlike those of the marginals are always 

 rounded or truncated at the end. These actinal spines of the 



