2 HAWAIIAN AND OTHER PACIFIC ECHINI. 



more or less widely separated above tlieir basal union. In size, the valves 

 show a wide ranLj;e, from less than lialt' a millimeter to over halt" a centi- 

 meter lonLr. tlie width beinac from .10 to .70 of the leni>;th. In small 

 examples the stalk, wliicli is a simple, straight rod, is often as long as 

 the valves, but in large ones the valves are much the longer. Tridentate 

 pedicellarite occur mainly around the primary spines, especially on the 

 actinal half of the test, but they may occur abactinally and are sometimes 

 conspicuous on the abactinal system. Tliey may be entirely wanting not 

 merely in individual cases but in wliole groups of species. 



The large globiferous pedicellaria3 are always three-valved. They take 

 their name from the fact tliat when tlie valves, which are lar<re and hollow, 

 are closed in their normal position, the wliole head appears more or less 

 globular. The cavity of each valve opens on tlie inner side near the tip, 

 or the opening may be terminal. The size of tlie opening is very variable, 

 but the three valves of any one pedicellaria are all alike. When the 

 opening is not at the end, the tip of the valve may be blunt and rounded 

 or it may terminate in a more or less conspicuous " end-tooth." When 

 the opening is large the edges are usually irregularly serrate, and more 

 or less of the entire length of the margin of the valve may be provided 

 with small teeth. The lower edge of the opening is usually sharply 

 indicated by a Iiorizontal, outwardly curved " lip," but this is frequently 

 imperfect or entirely wanting. The lower part and back of the valve is 

 more or less perforated with holes of variable size and shape. True large 

 globiferous pedicellari;o show relativel}^ little diversity in size, the valves 

 ranging only from one-half to a little more than one millimeter in length. 

 The stalk is usually about as long as the valves, but is often less, while 

 on the other hand it may be twice as long. Usually it is a simple, straight, 

 calcareous rod, but in some species there are frequently, if not always, 

 projecting, slender spicules which form a circle near the distal end of the 

 stalk; this is referred to as the "limb." Large globiferous pedicellarite 

 occur cliiefly on the abactinal lialf of the test and most commonly between 

 the primary spines, though they are often frequent on the abactinal system. 

 They seldom occur on the ambulacra or near the actinostome and they are 

 often entirely wanting, not merely in individual cases, but even in whole 

 groups of species. In individuals on which they are abundant, there may 

 not uncommonly be found large globiferous pedicellariie in which the 

 valves have become elongated and narrow, without a lip, and the opening 



