210 



iroius and Loxechinus to the P>hiiiida'; the relation of Slronf/ijlocentrolus 

 uppearod iinceiiaiii. tli()iii>h I liavc IhoiiiJiit it probably nearest related to 

 the r().\o|)neii.slida'. I idortunately, the larva' ol most ol' tliese f^enera are 

 still nid'Cnown: but we know those of Parucenlrolus lividus, Heliociduris 

 Inbi'iriildhi ( I he reduced larva of //. crijlhrof/ramma does not count in 

 this coiiiieilioH - ) and some "Slronfiijloccn I lal us" -species. 



'Vhv larva ol Pdidccnlrulus lividus agrees with I he fuhinus-iy])^: liie body 

 rod is elongated, (•luhsha])ed, and no basket slrniduie is found in the iirst 

 stage; thei'e is no posterior transverse rod or posterolateral |)roeesses in 

 the second stage. Anterior but no posterior epaulets (as in Psammfrhinus 

 miliaris). In the larva of Heliocidaris luhcrcultilii (he body skeleton in the 

 (irst stage forms a very complicate basket sli ndure, as in the Echinomelra- 

 larva : in Ihe second stage there is a posterior transverse lod and postero- 

 lateial lobes; vibratile lobes are present, but no e|)aulels. 



Within the genus SIroiif/ijlocenliolus we know the larva' of the species 

 drobarhiensis and (lauciscauus fairly completely, that of pulchrnimus nearly 

 so and that of purpuialus in its first stage. They all agree in the body 

 skeleton forming no basket-structure, the body rod being clubshaped. elong- 

 ate (less so in franciscdinis); in the second stage there is no posterior trans- 

 verse rod or posterolateral processes, but both anterior and posterior epau- 

 lets as in the Echinus-lnrya (presence of epaulets in [he pulchcrrimus-larvci 

 uncertain). 



To the genus Sliougijloccnlrolus Clark also refers the mediterranean 

 species (//7//)/;/f///'.s. otherwise unanimously regarded as the type of a separate 

 genus, SplKU'iechinus. According to my view this genus belongs to the 

 family Toxopneustida', repiesenting a polyporous development within that 

 family. The larva of this species dilTers most conspicuously from those of 

 the above named .S7/o/!_(////occ/i//o/f/,s-species. The body skeleton forms a 

 basket-structure in the first stage; in the .second stage a posterior trans- 

 verse rod is foiiiu'd. and there are posterolateral processes, vibratile lobes 

 and anterior biil no posterior epaulets. Thai Ihe posloral lods are fene- 

 strated is another conspicuous diU'erence from the Slroufiiilocculrolus-lavxx, 

 though of minor morphological im])ortance. Thus it is evident that the 

 characters of the larva of Sph. yniuularis bear decided testimony against 

 classifying that form with the "Strongylocentrotidae", or even referring it 

 to the genus Slroiu/ylocenlrotus itself, while on Ihe other hand there is per- 

 fect agreement between the larval characters of .S'. (//(Uiularis and those 

 of the other Toxopneustid-larv» thus far known. 



To the genus Slronf/ylocenirotus Clark also refers the .lajianese species 

 depressus, which, according to my view, represents the type of a separate 

 genus, Pseudocenlrolus, of the family Toxopneustida-. The little bit of in- 



