22 HAWAIIAN AND OTHER PACIFIC ECHINI. 



16-18) the primary spines are spatulate or swollen at the tip, at least abactinally. 

 In ravenelii, the primaries around the mouth (PI. 122, figs. 12, 13) are noticeably 

 modified. So far as the miliary spines are concerned, in audouini, japonicus, 

 leptostracon, rarispinus, and virescens, they are more or less swollen or club- 

 shaped at tip (PI. 122, figs. 8, 10), while in all the other species they are cylindri- 

 cal or terete (PI. 122, fig. /), though in lamprus, and in individual cases in other 

 species, some of them may approach the club-shaped form. 



The quadridentate pedicellariae (PI. 123, figs. 10, 11) have so far been found 

 only in ravenelii and subdepressus, but they will probably be detected in some 

 other species. Their valves (PI. 123, fig. 7) are narrow, compressed and meet 

 only near the tip. The tridentate have been found in all of the nineteen species 

 but they show considerable variety in form and in a few species (audouini, 

 australasiae, humilis, rotundus) they seem to be very scarce. The valves 

 may be broadly in contact (PI. 123, figs. 20, 21, 29) or meet only at the tip (PI. 

 123, fig. 1; PI. 124, fig. /); they may be long and narrow throughout (PI. 123, 

 figs. 15, 16) or expanded at the tip (PI. 123, figs. 2, 3, 12, 19; PI. 124, figs. 2-6), 

 or broad and somewhat leaf shaped (PI. 123, figs. 26, 27). In lamprus, the blade 

 is almost tubular and only a little expanded at the tip (PI. 123, fig. 22). The 

 ophicephalous pedicellariae (PI. 123, fig. 17) are less common than the tridentate 

 in most species and were not found at all in audouini, prostratus, and rotundus: 

 they were very scarce in australasiae and humilis. The opening of the blade 

 (PI. 123, figs. 4, 28) is broad and low and surrounded by conspicuous teeth. The 

 loops vary much in size and form in the three valves of the same pedicellaria 

 (compare PL 123, figs. 5 and 6 or figs. 18 and 14)- In many cases, the largest 

 valve has a notable bihamate loop (PL 123, figs. 8, 9, 30, 31), and these hooks 

 may even unite at the ends with the sides of the loop (PL 123, fig. 23). The 

 triphyllous pedicellariae (PL 123, fig. 18) are so small they are difficult to find, 

 and while they probably occur in all the species, I failed to find them in several. 

 The valves (PL 123, figs. 24, 25) are broad and flat with finely serrate margins. 



Key to the Spirits of Clypeaster. 



Margin oi U si very thick, the upper surface rising so uniformly from ambitus to madre- 

 porite thai a real margin can hardly be measured, hut even in Battened individ- 

 ual- it is rarely lese than .:;<* test-length; height of test rarely lees than :>." I 

 length; lower surface of test deeply com 

 I est ""I evenly convex above, the median area of petals being mon or less markedly 

 elevated, not only above the poriferous areas but above the interambulaera also; 

 pore-pairs in petals numerous (more than forty-five on each ride in an unpaired 



