Report on the Echinoderms of North-East Greenland. 253 



the possession of which is the cause of the specific name, and which 

 may he indifferently spoken of as a "vexillum"." Likewise Daniels- 

 sen and Koren write (Op. cit. p. 90): "The mesial spine (the apex 

 spine) is, usually, shorter than the lateral spines, and has a more 

 rounded form. It carries upon its extremity a kind of pedicel- 

 laria . . . . " 



I was at first somewhat puzzled at these descriptions. On exa- 

 mining the adambulacral spines of the present specimen, as well as 

 of other specimens at hand, on places where they were unhurt, I 

 found a simple median spine, resembling the figure of the vexillum 

 given by Grieg (Op. cit. PI. I, Fig. 1); but this spine I found to be 

 attached directly to the adambulacral plate, while, according to the 

 descriptions, it should be attached to a shorter spine, which should 

 again be attached to the adambulacral plate. 



The figure of the "vexillum" given by Bell (op. cit. PI. XXIV, 

 Fig. 1) is evidently such a spine, differing from the usual median 

 spine in being broken at both the upper and lower end, while the 

 figure given by Grieg represents a complete spine, and it is not 

 quite reconcilable with the description, as it is evidently not inserted 

 on a lower spine but directly on the adambulacral plate. — There 

 is, evidently, no other explanation of the "vexillum" than that it 

 is the broken point of the median adambulacral spine, 

 the short inner spine to which it is said to be attached being 

 the basal part of the broken spine. The description given by 

 Wyville Thomson (Op. cit. p. 151): "The inner spine of each 

 comb on the side of the adambulacral groove is longer than the 

 others, and bears on the end a little oblong calcareous plate usually 

 hanging from it somewhat obliquely like a flag, with sometimes a 

 rudiment of a second attached to it in a gelatinous sheath, which 

 makes it probable that it is an abortive pedicellaria", thus is very 

 naturally explained. This adambulaeral spine is, indeed, very fragile, 

 and I have myself seen such as were broken both once and twice, 

 the pieces hanging in the somewhat thick skin of the spine, but I 

 was never in doubt that they were broken spines; probably all these 

 spines were broken in Wyv. Thomsons specimens, otherwise he 

 would scarcely have been misled. Grieg, on the other hand, was 

 misled by the wrong descriptions, so that he gave an incorrect 

 explanation of his quite correct observations. — In fact, it cannot 

 be doubted that the "vexillum", which was regarded as so peculiar 

 a structure, is nothing but the flattened inner adambulacral spine — 

 or its broken point — and there is no reason for having a special 

 name for it. In PI. XIV, Fig. 5 I have represented the inner promi- 



XLV. 18 



