88 Dr. Til. Mortensen on some EchinothunJs 



the valves are apart, though not so -widely as in A. varium 

 and Gruhei (in A. urens and Jieteractis * this form of pedicel- 

 laria is not known), joining only at the point. The edge of 

 the outer ])art is a little sinuate, thus faintly indicating the large 

 .•linuations found liere in the other species (comp. 'Ingolf 

 Ech. pi. xiv, fig. 7) ; in the pcdicellariae from the actinal side, 

 liowcver, the sinuations are more developed, but only the 

 cuter one on each side, two deep sinuations being never found 

 as in the other species. These pedicellariae thus afford a very 

 distinct character for this species. The blade is filled with a 

 coarse nieshwork ; the edge is irregularly serrate, also along 

 the unusually thick basal part ; the neck is short. Those 

 found on the abactinal side are green-coloured. 



The second form of tridentate pedicellarise (PI. V. figs. 1, 

 13, 14) is more lichly develojjed than in the other species, 

 pcrha])S on account of the absence of one form ; they occur 

 in vcrj^ difierent sizes, the larger ones reaching the same siz3 

 as the first form. 'J'he valves are long and narrow, joining 

 in their whole length. The blade is provided with a toothed 

 median keel, and otherwise, especially in the larger pedicel- 

 lariaB, filled with a coarse meshwork. In quite small ones 

 there is only little meshwork. The edge is finely serrate, 

 stiaight in the small specimens, with some sinuations in the 

 cuter part in the larger ones. These pedicellaria; occur 

 en both sides of the test, those on the abr.ctiual side generally 

 larger and gieen, like the other foim of tridentate pedicellarise. 

 The neck is well developed. 



The trij)hyllous pedicellarise (PI. Y. fig. 3) have a long 

 open slit in the cover-plate, as in the other species of the 

 genus, but the form is somewhat difierent, the outer part 

 being bioader than in those species (comp. * Ingolt ' Ech. 

 pi. xii. fig. 18). 



The spicules (PI. V. fig. 10) are somewhat more nume- 

 jous and a little larger than in the other speciis, especially 

 1( wards the sucking-disk. The spha;ridife continue on the 

 abactinal side almost to the apical system. 



'J he primary actinal spines are almost \\hife, not banded 

 as in the other ."species of this genus. The abactinal spines 

 are coloured alike in both areas, and in none of them is the 

 enclosing skin annularly constricted. The secondary spines of 

 the actinal side are thorny in their outer half, not " mostly 

 £mcoth,'^ as stated by Yoshiwara. 



" The most prominent feature by which this species can be 



♦ In a sj:eciiren of A. hettradis just recehed from Singfipoie (dredged 

 bv Mr. Gad) I find the laipe ioim of tridentate pediceJlaiia to occur. It 

 if quite like that of -<4. varix.m. 



