139 



Species a. (PI. XXIV, Fig. 3; Fl. XXV. Fig.!). The posterolaleral 

 arms are fairly uiMight; they are about lour times llie body ienglh, con- 

 siderably h)nger Ihaii the three inner pairs of arms, which are scarcely 

 twice the body lenglli. The preoral cihated band is straight, bending 

 abruptly downwards at the sides. The frontal area is distinct. 



Fig. 66. Skeleton of Ophiopluteus undulatiis. 



\. species a: 



B. species a, var. (olT I'ulo Pisang); C. species b. Letters as in Tig. 61. 



B/ 



Fig. 67. Part of 

 posterolateral rod 

 of Ophiopluteus un- 



dulatus. '»"/,. 



A. H. from typical 



form of species a: 



(",. from an aljnorm- 



al (?) s])ecimen. 



The skeleton (Fig. 66, A; Fig. 67. .\, B). The body 

 rods are rather strongly curved, the end rods very short, 

 rounded, with three or four short prominences. The 

 transverse rods are short and thick, forming together 

 a small arch; the ends of the transverse rods abut on one another quite 

 simply, without any sort of widening or indentations. The undidations of 

 the posterolateral rods begin at about the level of the postoral ciliated 

 band and continue unto the point; in the outer part the undulations are 

 somewhat longer. A few short, straight thorns are found on the top of 

 each undulation on the adoral side, sometimes also on the outer side. 



18* 



