141 



side and then, during growth, transferred to the ventral side, as was 

 stated by Ludwig.^) 



Species b. (PI. XXV, Fig. 2). This species is characteristic mainly by 

 its remarkably short posterolateral arms, which are shorter than the 

 anterolateral arms, and also broader, the vibratile band along them being 

 distinctly broader than on the other arms. The posterior edge of the body 

 is more rounded than in species a, quite semicircular, the body skeleton 

 not at all projecting beyond the line formed by the posterolateral rods. 

 The body is very short and broad, though perhaps hardly so low as shown 

 in the figure; especially the frontal area may be somewhat higher in the 

 living specimens. — The skeleton (Fig. 66, C) differs only very little from 

 that of species a. The transverse rods are slightly widened at the end, 

 and the end rods appear to differ somewhat in the shape of their thorny 

 outgrowths. 



Only two specimens, both in a poor state of preservation, are at hand, 

 from the Gulf of Aden (12° 48' N. 50° 23' E. 27/XIl. 13) and from off the 

 East end of Sokotra (28/XIl. 13). Both specimens agree in the characters 

 pointed out, so that it seems beyond doubt that this is a separate species, 

 not an individual abnormality. It should especially be emphasized that 

 there is no doubt regarding the peculiar character of the posterolateral 

 arms; the skeletal rod is complete, not broken, and although none of the 

 two specimens are so far in their development as to have begun meta- 

 morphosis, there is no reason to expect that the posterolateral arms would 

 ultimately reach the same length as in the other species. 



The fact that the body skeleton (Fig. 66, C) has the recurrent rod devel- 

 oped only on one side is, of course, an individual abnormality; in the other 

 specimen there is also a slight abnormality in the recurrent rod, but in 

 this case it is on the right side. 



Species c. (PI. XXIV, Fig. 2). This third species has a considerable 

 resemblance to species a. The posterolateral arms are long as in that species, 

 but more divergent; the arms are, upon the whole, relatively shorter than 

 in species a. Also the body is shorter and broader, and the frontal area 

 is mainly confined to the edges. (The figure is drawn from a fairly well 

 preserved specimen, so that it is not likely to be much different in the 

 hving specimens). In the skeleton (Fig. 68) only small differences from 

 species a are to be noticed; the body rods and the transverse rods are 

 more straight and the end rods have apparently only one small process 

 on each side. 



1) H. Ludwig. Jugendformen von Ophiuren. Sitz.ber. kgl. Preuss. Akad. d. Wiss. 

 Berlin. 1899. p. 212. 



