153 



Fig. 81. Skeleton of Ophiopluteus formosus, species c. ^""/i. 



Species c. In a plankton sample taken by Mr. Gruelundin the neigh- 

 bourhood of the Cape Verde Islands at 16ni' N. 21° 57' W. 14/Vl. 1920, 

 a single specimen of a larva of the 0. /ormosus-type was found. It is in 

 a very poor state of preservation, only the body skeleton and the postero- 

 lateral arms being intact. These parts, however, clearly show that we 

 have here another, distinct species of the formosm-type, which may be 

 easily recognized by 

 the characters of 

 its skeleton, even 

 though the shape 

 of its body is un- 

 known. 



The skeleton (Fig. 

 81) differs from that 

 of species a and b 

 mainly in the pec- 

 uliar shape of the 

 end rods, the points 

 of which are bent 

 nearly at a right 

 angle; they are 

 longer than in the 

 two other species 

 and also provided 

 with longer side- 

 branches. One of 

 the transverse rods 

 carries a short pro- 

 cess, which is, however, broken, so that its total length and the shape of 

 its point cannot be ascertained ; but it is evidently very nearly as shown in 

 the figure. The point of issue of the posterodorsal rod is not so close to 

 the base of the anterolateral rod as in the other species. (Apparently the 

 distance is not the same on both sides; this, however, is due to the fact 

 that the right one is broken and lies in a somewhat different position). 

 The thorns on the posterolateral rods are finer and more distant than in 

 species a and b. (Fig. 82). The posterolateral arms are very long and much 

 diverging. 



The occurrence of this larval type in the Red Sea, at Panama and in 

 the Atlantic Ocean is, of course, of importance, but it is not sufficient for 

 venturing on a suggestion as to the Ophiurid to which it belongs. That 

 Ophiopluteus formosus and similis are nearly related is fairly evident, the 



20 



Fig. 82. Part of posterolateral rod of Ophiopluteus formosus, ^"/^ 

 A. of species a; B. of species b; C. of species c. 



