146 



The skeleton (Fig. 72). The posterolateral rods are canaliculate from 

 about the middle unto the point. They are provided with small thorns, 

 somewhat irregularly placed, along both the outer and inner sides (Fig. 

 73, A). The other rods are smooth or only here and there with a very small 

 thorn. The transverse rods have a small thorn directed forwards and a 

 somewhat larger one projecting backwards; the ends of the transverse rods 

 are only slightly widened. The dorsal extra rods are a little thorny. 



Only a single, not very well preserved specimen of this larva is at hand, 

 taken off Koh Kam, in the Gulf of Siam, 4/II. 1900. 



al 



B 



Fig. 72. Skeleton of Ophiophiteus opulentus, species a. 290 /i. 

 Letters as in Fig. 61. 



Fig. 73. Outer part 



of posterolateral 



rod of Ophioplu- 



teus opulentus; 



A. species a; 



B. species b. 290 /i. 



Species b. There are two specimens from off the East 

 end of Sokotra (28/XII. 1913), both in so poor a condition 

 that no whole figure can be given of this larval species. It can only be 

 stated that the general form appears to correspond to that of species a. 

 The skeleton (Fig. 74) affords some' very good characters distinguishing 

 it from the former species. The posterolateral rods are entirely smooth 

 along the outer side (Fig. 73, B) and the canal goes almost from the base 

 to the point of the rod. The processes from the transverse rods are 

 directed more outwards in one of the specimens. 



Species c. (PI. XXII, Fig. 3). The relative length of the body and the 

 interior pairs of arms about as in species a, but the posterolateral arms 

 are conspicuously longer, about three times the length of the interior arms. 

 The frontal area appears to be rather larger than in species a. The preoral 

 vibratile band is somewhat upwards curving, while in species a it is nearly 



