166 



from the posterior end of the body to the point of the anterolateral arms. 

 Several species of this larval type are at hand. 



Species a. (PI. XXIX, Fig. 1). The length of the body from the post- 

 erior end to the frontal edge is ca. 0.34 mm. The frontal area is rather 

 large. The postoral band may curve much downwards, as seen in the 

 figure; this is, however, no constant feature and, evidently, to some 

 degree at least, depends on preservation. The preoral band curves upwards. 



Fig. 91. Skeleton of Ophiopluteus pusillus, species a. Letters as in fig. 85. 



but remains straight in the middle part. The posterolateral arms are about 

 1^2 body length. There is no distinct widening at the point of the arms. 

 The body skeleton (Fig. 91) is slender, the meshes being rather large, 

 rectangular; the end rods are fairly long and slender, with one or a few 

 small side branches somewhat above the tip, which is very gently curved ; 

 the outer edge near the point may be finely serrate. There is no process 

 from the recurrent rod. The posterolateral rods are provided with short 

 thorns of about equal size on both the outer and the inner side, the postoral 

 and posterodorsal rods with small thorns, placed mainly along the ventral 

 side of the former and along the dorsal side of the latter, so as to appear 

 mainly as transverse lines on these rods in ventral or dorsal view of the 

 larva. 



