142 



One specimen of this species was found off Taboga, in the Gulf of Pa- 

 nama, in December 1915. Another specimen from the same locality very 

 probably also belongs to this species; it is, however, abnormal, the right 

 posterolateral arm being quite short, while the left is normally developed. 



Also the postoral arms 

 are quite short and 

 rudimentary. The body 

 is considerably smaller 

 than in the normal 

 specimen. 



Besides this species 

 there are two more 

 larvse from the Gulf 

 of Panama (November 

 and December 1915) 

 which appear to repre- 

 sent two more species 

 of the undulatus-tyipe, 

 related to species b. 

 As they are not in a good state of preservation, 1 do not think it worth 

 while describing them, the main thing being the fact already sufficiently 

 established that there are several distinct species within the undulatus-type. 

 The fact that this larval type occurs both at Panama and in the Indian 

 Ocean affords an important indication for the determination of the Ophi- 

 urid to which it belongs. It may be concluded that it must be a type 

 represented by more than one species both in the Indian Ocean and at 

 the tropical west-coast of America. However, it would hardly be advisable 

 to speculate more on this question at the present state of our knowledge. 



Fig. 68. Skeleton of Ophiopluteus undulatus, species c. """/i. 



Ophiopluteus fulcitus nova forma. 

 The outstanding feature of this larval type is the branch proceeding 

 obhquely upwards from the postoral rod towards the postoral vibratile 

 band, giving thus a skeletal support to the anal area. There may be one 

 or two more processes from this rod, situated farther down. The antero- 

 lateral rod is furnished with distinct, curved thorns along its outer side 

 from about the level of the frontal area. The posterolateral rods are pro- 

 vided with large, curved thorns along the inner edge. The postoral and 

 the posterodorsal rods are smooth or finely thorny. Body skeleton com- 

 pound; the transverse rods nearly straight, hardly widened towards the 



