167 



A dozen specimens of this larva were found in a plankton sample from 

 Misaki, Japan, 17/VI. 1914. A specimen from off Koh Kam, Gulf of Siam 

 (4/II. 1900) differs from the Japanese specimens in lacking the small side- 

 branches of the end rods, but otherwise so closely resembles the latter 

 that I have no doubt in. referring it to the same species. 



Species b. (PI. XXIX, Figs. 2 — 3). This species agrees with species a 

 in the character of the spinulation of the posterolateral and the other rods. 



Fig. 92. Skeleton of Ophiopluteus pusillus, species b. ^m/^. 



but differs markedly from the latter species in the shape of its body 

 skeleton (Fig. 92). The meshes are not quite rectangular, but generally 

 distinctly narrowing downwards, and there is a conspicuous process from 

 the recurrent rod. The transverse rods are somewhat longer than in species 

 a, in accordance with the insertion of the recurrent rod nearer the body 

 rod. The end rods are somewhat shorter and quite straight, and the side 

 branches are placed close to the tip. Otherwise it agrees very closely with 

 species a in its general shape, only the postoral and posterodorsal arms 

 being still somewhat shorter; they reach only to about the level of the 

 preoral band. 



A very interesting stage of metamorphosis is represented in PI. XXIX, 

 Fig. 3. As in Ophiopl. formosus, sp. a (PI. XXX, Fig. 2) and 0. undulatus, 



