133 



of the arms are perfectly smooth. The posterodorsal rods issue very near 

 the base of the anterolateral rods; they are slightly widened at their base. 



Five specimens of this larva were found in a plankton sample from off 

 Taboga, the (iulf of Panama, taken in November 1915. 



Among some larva; presented to me many years ago by Frof.V. Hensen, 

 Kiel, collected in .January 1897 in the fiismarck Archipelago, there are a 

 few specimens of this same larval type. Ihifortunately the skeleton has 

 been dissolved, and as the preservation is also otherwise poor, I shall give 

 no description of these larva?; but it is evident that we have here another 



F"ig. ,')8. Skeleton of Oplnupluleus of Ophiocoma, species b. -""/i- Letters as in fig. .5.3. 



species of Ophioconm-lavwA, clo.sely related to and very similar to species 

 a and b, but difl'erent from both, of course, since there is no species of 

 Ophiocoma common to these seas. 



Species c (PI. XXX, Fig. 1). The shape of the body differs consider- 

 ably from that of species a and b. the hind end of the body being not nearly 

 so broad and Hat as in those species; further the vibratile lobes are much 

 less developed. (In the figure the two ventral ones are directed outwards 

 and thus rather inconspicuous). The body is fairly elongated, the frontal 

 area large. The preoral ciliated band forms a high arch, and the postoral 

 band curves somewhat downwards in the middle, besides nuiking a slight 

 sinuation at each side. The arms arc all short, the posterolateral ones only 

 slightly exceeding the body length, the other arms merely about half the 

 length of the body. They are all fairly broad and ilat, but hardly widening 

 at the point. 



The skeleton (Fig. 59) is much more like that of Ophiocoma echinata 

 than that of species a and b, the body rods being not horizontal, but rather 

 inore erect than in O. echinala. The posterolateral rods are slightly widened 

 a little beyond the base (Fig. 60). The transverse rods are less widened 

 than in species b, and the end rods are directed straight downwards, while 

 in species b they are medially directed like the transverse rods. The rods 



