165 



Malacca Strait, off Pulo Pisang, 1/XII. 1899 (1 specimen) and 101 12' E. 

 2 45' N., Malacca Strait, 30/XI. 1899 (6 specimens). 



Species b. (PI. XXII, Fig. 2). The inner arms are distinctly shorter 

 than in species a, only of about body length, and especially the postoral 

 and posterodorsal arms are conspicuously shorter than in species a. The 

 backward process from the posterolateral rods is much shorter than in the 

 former species and has only very few serrations; sometimes it is quite rudi- 

 mentary; there is no process from the body rod, and the median process 

 from the transverse rods is quite short. The anterolateral rod is provided 

 with rather large thorns along the outer side (Fig. 90). The specimen figured 

 presents a series of well defined spots in the vibratile bands along the 

 arms, especially the posterolateral ones. Most probably these are pigment 

 spots; but this can only be definitely ascertained by the study of living 

 specimens. 



This species was found off Jolo, 20/111. 1914 (1 specimen) and off Co- 

 lombo, 13/11. 1898 (6 specimens) (Mr. H. Mortensen). 



It is not quite easy to distinguish this species from 0. pusillus species c, 

 and the possibility cannot be denied that both are really the same, very 

 variable species; the fact that they were taken together (Colombo, 13/11. 

 1898) would also point in this direction; but no definite conclusion can be 

 reached from the preserved material, and I have thought it preferable 

 to keep them as two separate species in view of the marked difference 

 between typical specimens. 



A suggestion as to the Ophiurid genus lo which these larva- belong, 

 cannot be made for the present. 



Ophiopluteus pusillus nova forma. 



The characters which distinguish this larval type are the following. The 

 body skeleton is of the compound type, often with a process from the 

 recurrent rod; the transverse rods are slightly widened at the point, with 

 some short obtuse prominences, fitting into one another; no median pro- 

 cess. The anterolaleral rod is set with rather coarse thorns along the outer 

 side in the outer part. The posterolateral arms are rather short, only about 

 twice the body length, not much outwardly directed: the anterolateral 

 arms are somewhat less than body length; their points are at about the 

 level of the points of the posterolateral arms. The postoral and the postero- 

 dorsal arms are much shorter than the other arms and hardly reach beyond 

 the frontal edge. Characteristic of this larval type is also its small size, 

 which, in the fully formed larva, is only ca. 0.5 0.7 mm in total length, 



