236 HAWAIIAN AND OTHER PACIFIC ECHINI. 



The Spines, PEDicELLARiiE, SpHiERiDiA, and Spicules. 

 Plate 93, figs. 1-15, 22, 23, 32. 



The spines of the Echinidse are smooth and soHd and afford few characters 

 of value for systematic purposes. Generally there is no very marked difference 

 between the primaries, secondaries, and miliaries, but in a few cases the primaries 

 are conspicuously longer. As a rule the primaries are relatively short and stout 

 but in a few cases they are long, slender, and pointed. The secondaries also are 

 usually rather short and stout, but are occasionally very slender and sometimes 

 are noticeably rough. 



The pedicellaria3 of the Echinida show considerable diversity, all of the four 

 kinds being more or less common. The following summary of their characters 

 is necessarily largely a repetition of the very complete publications of Mortensen. 

 The globiferous pedicellarise are remarkable for the very great development of 

 poison-glands in connection with the valves. These glands may be on the stalk 

 or on the valves of the pedicellarise, but in either case are commonly quite con- 

 spicuous. They may be present in both positions. The stalks themselves are 

 made up of slender calcareous threads, which are only very slightly connected 

 with each other; or the threads may be stouter and very fully united together 

 making either a somewhat tubular or a solid stalk. In some cases the head is 

 connected with the stalk by a neck of greater or less length but often the neck 

 is wanting. The valves show a greater or less specialization in the different 

 species, the most specialized valves being found in those species which have some 

 specialized condition in the test. In their simplest condition, the valves have 

 the blade open, but more or less deeply concave and in addition to the terminal 

 tooth which is of moderate size there are additional teeth on each lateral margin. 

 In a slightly advanced condition the terminal tooth is larger, there are only one 

 or (wo {vc\h on each side and there are cross-bare of lime connecting the margins 

 of (li{> somewhat compressed blade. Further specialization occurs by the closer 

 and more ('onij)lc(o union of ihe margins and the developineiit of tlie terminal 

 tooth with \\\v a('('om|)anying reduction or loss of the lateral teeth. In the most 

 specialized condition tiie blade is cylindrical and terminates in a single very 

 prominent tooth, but in other cases, there is a very large lateral tooth on the 

 left side, slightly below the tip. Sometimes, in species which typically have this 

 unpaired tooth, valves with a similar but somewhat smaller tooth on the right 

 (PI. 95, fig. 24) are fouml. The steps by wliich the transformation from the 



