162 Proceedings of the Royal Physical Society. 



my examples, the colour of one exactly fits Koehler's statement in the 

 original description (1898) of 0. insidiosa, "La couleur generale est gris- 

 bleuatre " (p. 92) ; while of the other it may be said with equal truth, as 

 Koehler says of 0. foveolata in the "Siboga" expedition reports (1905), "La 

 coloration generale est jaunatre ou legerement rosee " (p. 77). The spines 

 on the interradial and central plates of the dorsal disc-surface are fewer 

 and shorter in one of my examples than in the other. But as there is 

 undoubtedly considerable variation in what is now regarded as 0. foveolata, 

 it is sufficient for me to add that my identification of 0. insidiosa is admitted 

 by Koehler, and that he adds, " 0. insidiosa Koehler est synonyme de 

 0. foveolata- Marktanner-Turneretscher ainsi que je l'ai reconnu." 



Localities. — St. XXII , Hastings Harbour, St Luke's Island, 3 to 20 

 fathoms and shore, rock and sand (one example). St. XXX., Fly Island, 

 Observation Island and south-west of Domel Island, 8 to 15 fathoms, rock 

 and sand (one example). 



An example of this species was taken by the " Siboga " expedition at a 

 depth of 141 metres. This seems an exceptional case. Previous records 

 for the Indian Ocean are from the Andaman Islands and from the south of 

 Ceylon. 



(8) Ophiothrix martensi Lyman, 1874. 



This species is represented by a single example, with arms broken at 

 about 25 mm. from the disc, and with a disc-diameter of 8 mm. Lyman (1874), 

 after describing his type, which had a disc-diameter of 14 mm. and an arm- 

 length of 63 mm., gives (p. 235) some points of difference observed in " a 

 smaller specimen with a disc of 6 - 5 mm." My example, as the size might 

 indicate, approaches more closely to Lyman's description of his smaller 

 specimen than to that of his type. In the type " the disc is covered by 

 thick skin which obscures the outline of the radial shields and nearly hides 

 the scaling" (p. 235). The smaller specimen "had a thinner skin so that 

 the various parts were better defined" (p. 235). If there is any skin 

 covering the disc in my specimen it must be exceedingly thin, for the 

 scaling is very distinct. The radial shields, which are smooth, are triangular 

 in shape, with a notch in the base, and each is separated from its fellow by 

 a single row of about four elongated scales, coloured blue along the centre, 

 and with the margins white. This blue line stretches along the arm, on the 

 middle line of the dorsal arm-plates. In the centre of the disc there is a 

 large circular plate surrounded by several circles of much smaller scales. 

 Between the radial shields, iu the interradial space, there are four rows of 

 oval scales radiating from the margin of the disc to the smaller scales 



