30 



and it was thus impossible to rear the larva. Nevertheless I can give some 

 description of this larva. In some plankton samples from Taboga from 

 November and December 1915 I find three specimens of an Arbacud- 

 iarva Since Arb. stellata is the only species of the Arbacud. known 

 to occur in the Gulf of Panama^), and since young specimens of this 



Fig. 5. Skeleton of larva of Arbacia stellata. ^^o/^. To the right side is represented separately 



part of the outer end of the postoral rod. 



al. anterolateral rod; b. body rod; da. dorsal arch; pd. posterodorsal; pi. posterolateral; 



po. postoral; ptr. posterior transverse; r. recurrent rod. 



species were fairly common in the said locality, there can be no doubt 

 that this larva does really belong to A. stellata. 



None of the three specimens are quite fully developed, but the specimen 

 figured is in a sufficiently advanced stage to give the proof of the import- 

 ant fact that the larva of this species conforms closely with the two other 

 A/'ftacm-larvse hitherto known, viz. of A. lixula and pundulata. The 



1) It may perhaps hardly be possible to distinguish with certainty the young specimens 

 of A. stellata from those of A. spatuligera; siinc, however, the latter species is not found to 

 the North of Guayaquil, there can be no question of the identity of these young specimens 

 from Taboga with A. stellata. 



