135 



somewhat erect and very long, much longer than the inner arms; the 

 posterolateral rods are strongly thorny along the inner side, more or less 

 canaliculate. 



Species a. (PI. XXI, 

 of the body is somewhat 

 ionally high, the distance 

 to the anterior edge being 

 the postoral band to the 

 preoral band is some- 

 the middle. The postero- 

 the body length, the 

 than body length; the 

 ly longer than the post- 



Fig. 1). The body length is 0.4 mm. The shape 

 unusual through the frontal area being except- 

 from the preoral ciliated band 

 about half the distance from 

 posterior end of the body. The 

 what downwards produced in 

 lateral arms are ca. five times 

 other arms only a httle more 

 anterolateral arms are distinct- 

 oral and posterodorsal arms. 



Fig. 61. Skeleton of Ophiopluteus costatus, a. ^so/j. a. accessory rod; al. anterolateral rod; 

 b. body rod; dm. dorsal median process; e. end rod; pd. posterodorsal; pi. posterolateral; 

 po. postoral; pr. preoral rod; r. recurrent rod; tr. transverse rod; vm. ventral median process. 



There appears to be no swelling at the point of the arms. Pigmentation 

 unknown. 



Skeleton (Fig. 61). The body skeleton is fairly robust. The transverse 

 rods are short and thick ; from one of them proceed on the ventral side a 

 short, pointed median process, and on the dorsal side a much longer, simple 

 rod, the dorsal median process. A smaller process is directed backwards, 

 with a small side branch near the end; there is one both on the ventral 

 and on the dorsal side. The end rods are short, trifid. The posterolateral 

 rods are set with thorns along their inner sides ; they are pecuhar in having 

 what looks hke a narrow canal in the lower part, reaching from the first 

 thorn until about the middle, where it ends with a small swelhng in one 

 (the right) arm, while in the left arm it passes some way beyond this point 



