59 



Echinopluteus of Temnopleurid (?), species b. 

 From the Gulf of Siam (off the North of Koh Kut, 27/1. 1900), there 

 are two larvae in an advanced stage of metamorphosis, which represent 

 another closely related species (Fig. 21). The posterior transverse rod 

 is shorter and the lower branches have fewer thorns than in species a; 

 the small inner branches are lacking. The irregularities of the upper 

 branch seen in the figure are, evidently, abnormal; they are not seen 

 in the second specimen. The posterodorsal rod is distinctly curved 



Fig. 21. Skeleton of Temnopleurid larva, species b; front view. -^Vi- Tlie widening of the 

 dorsal and ventral transverse rods are probably due to the beginning metamorphosis. 



Letters as in fig. 20. 



and, like the postoral rods, densely serrate. Both these rods are fene- 

 strated in their whole length. The dorsal arch has the same shape as in 

 species a, only the posterior prolongation appears to be shorter. In one 

 of the specimens muscles are seen very distinctly to pass between the 

 ends of the body rods, which proves that the four main arms in this 

 species may be moved and probably are kept in a nearly horizontal posi- 

 tion while swimming, as in the Mespilia-iarva. That vibratile epaulets 

 are present as in the Mespilia-lsLYva can be ascertained, otherwise the 

 shape of the larval body cannot be seen distinctly on account of the ad- 

 vanced stage of metamorphosis. 

 As with species a it can only be said that, judging from the close resemb- 



8* 



