88 Dr. Til. Mortensen on some Echinolhuvids 



tlie valves are apart, though not bo widely as in A. vurium 

 and (jrubei (in A. urens and heferactis * tiiis form of pedicel- 

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

 the outer part is a little sinuate, tlius faintly indicating the large 

 .'^innations found here in the other species (comp. 'Ingolf 

 ]Cch. pl.xiv. fig. 7) ; in the pedicoUarise from the actinal side, 

 however, the sinuations are more devcloited, but only tho 

 nnter one on each side, two deep sinuations being never Ibund 

 as in tlie other ppccies. These pedicdlarise thus afford a very 

 distinct character for this s])ecies. The blade is filled with a 

 coarse mcshwork ; 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. 



1'he second form of tridentate pedicellariae (PI. V. figs. 1, 

 ]3, 14) is more richly develojjcd than in the other species, 

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

 in very difi^crent sizes, the larger ones reaching the same size 

 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- 

 ]aria3, filled with a coarse meshwork. In quite small ones 

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

 Btiaight in the small specimens, with some sinuations in the 

 outer part in the larger ones. These pedicellariai occur 

 on both sides of the test, those on the abf.ciinal side generally 

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

 The neck is well developed. 



The tri])hyllous pedicellarise (PI. V. fig. 3) have a long 

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

 gerus, but the form is somewhat different, the outer part 

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

 pi. xii. fig. 18). 



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

 rous and a little larger than in the other sjjcciis, especially 

 t( ^vards the sucking-disk. The sphajridife continue on the 

 abactinal side almost to the ajjical .system. 



'i he primary actinal spines are almost while, not banded 

 as in the other f-pecies of this genus. The abactinal spines 

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

 enclosing .'■kin annularly constricted. The secondary spines of 

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

 gnicoth,'' as stated by Yoshiwara. 



" The most j;romincnt ieature by which this species can be 



* In a Efecimen of A. hetd-actis just received from Singf.poie (dredged 

 ty Mr. Gad) 1 find ihe Jaipe lorm of tridentate pedicellaiia to cccur. It 

 it quite lite that oi A. vanum. 



