CLYPEASTRINA. 13 



The Spines, Pedicellaiuae, Sphaeridia, and Spicules. 

 Plates 122-125.' 



In all clj'peastroids the test is densely covered with spines. Occasionally- 

 one can distinguish three very distinct sizes of spines, which might he called 

 primaries, secondaries, and miliaries, but since these so-called primaries are 

 present in very few species and are not surrounded by circles of secondaries, it 

 has become a general custom to speak of the spines of clypeastroids as "pri- 

 maries" and "miharies" only, the term "secondary" not being used. We 

 therefore speak of the conspicuous spines in such species as Clypeaster lamprus as 

 "large primaries." Occasionally one finds the term "secondary" but it is used 

 simply as a synonym of miliary; thus de Meijere, in his notable account of the 

 clypeastroids of the Siboga (1904, Siboga Echini, p. 103-139) occasionally refers 

 to " secundarstacheln " but in every case the context shows that he means 

 miliaries. It was due to his careful work that attention was first called to the 

 characteristics of the miliary spines in the Laganidae and the striking difference 

 there is between them and those of the Clypeastridae. Apparently de Meijere 

 has gone too far in attempting to find specific and generic characters in the 

 mihary spines, for examination of these spines from nearly all the known species 

 of Laganidae has satisfied me that there is so much individual diversity and so 

 much evidence of varying degrees of wear on the tips of these spines, that they 

 are of little real value for specific distinctions. But the fact remains that the 

 form and structure of the terminal portion of both primary and miliary spines 

 in clypeastroids are characters of real importance in working out the interrela- 

 tionships of the genera. 



In all the genera, the primary spines are solid, but they may be either 

 straight (PI. 122, figs. 9,11,16,17), curved (PI. 122, figs. 12, U) or bent (PI. 125, 

 fig. 16); they may taper to a sharp point (PI. 122, fig. 9) or be quite blunt (PI. 

 122, fig. 16), or be flattened and chisel-Uke (PI. 122, figs. 12, 13), or simply 

 expanded (PI. 122, fig. 1) or be much swollen at the tip (PI. 125, figs. 4, 5, 17, 18) ; 

 they may be quite smooth (PI. 122, fig. 16) or serrated along one side (PI. 122, 

 fig. i4) or more or less rough with serrations on all sides (PI. 125, figs. 4, 5) ', they 

 are commonly longitudinally striated, the striations being raised as more or less 

 evident ridges, which may be quite serrate; there is sometimes a marked differ- 

 ence between base and tip of spine in the smoothness or roughness of its surface. 



' The numeration of the plates is continuous throughout the reports on the Hawaiian and other 

 Pacific Echini (Memoirs M. C. Z., 34j 



