cellariae of the same nature as those which in great numbers cover all the cuticular sheaths 

 of the spines. But besides these soft transverse ridges, there appear in the interior or 

 adoral part of the arms, to about V4 of their length, a number (10 — 14) of transverse ribs 

 separated by gi-eater intervals of quite a different nature, namely like strongly projecting 

 solid calcareous beams, which from both sides of the skeleton on the underside of the arms 

 extend at tolerably regular intervals round the dorsal side of the arm, stretching the soft 

 dorsal skin over the interior organs that lie beneath. Along these calcareous transverse 

 ribs (which often (see Tab. II, fig. 4) project very strongly keelshaped on each side, giving 

 to part of the lateral outline of the arms an irregularly sinuous appearance) there is attached 

 a row of more or less elevated spines increasing in length outwards or towards the sides, 

 whereby a certain number of very conspicuous rings of spines are produced over the basal 

 part of the arms, a feature which is very characteristic of the present species, and has also 

 given rise to the specific appellation coronata. 



If the animal is viewed from the lower side (Tab. I, tig. 2 & 5) there will be seen 

 in the middle a naked membrane (the bucal membrane) circumscribing in the centre a more 

 or less ample circular aperture (0 (the bucal aperture) through which the digestive cavity 

 may be seen. On the sides, this naked and altogether soft part is enclosed in a narrow 

 circular frame of calcareous consistency. This bucal frame, which is formed of the peripheral 

 part of the disc, is not even, but exhibits alternately elevated and depressed surfaces. The 

 former (fig. 5, d. d.) which always lie in the direction of the interval between two arms, are 

 covered with a certain number of rather symmetrically arranged spines of unequal size, which 

 hke the spines on the arras, are enveloped in a cuticular sheath thickly covered with pedi- 

 cellarise; the innermost of these spines (usually 6 in number) form at the end of the elevated 

 space a fanlike fascicle turned inwards towards the mouth. The depressed spaces of the 

 bucal frame (ibid. c. c.) which are always found just before the insertion of the arms, form 

 the immediate continuation of the wide and deep ambulacral furrows (comp. fig. 2) which 

 run along the whole length of the arms, and at the bottom of the depression there are 2 

 pairs of tentacles or water-feet extending forwards between the spines on each side. After 

 these 2 pairs of water-feet belonging to the disc, come the water-feet belonging to the arms 

 arranged continuously in the same manner, and at the same distances from each other, and 

 thus forming with those first mentioned 2 uninterrupted rows. On each side of the ambu- 

 lacral furrow of the arms, and issuing from the thickened border which forms their lateral 

 boundary, being itself formed of the lateral parts of the ambulacral skeleton, are the very 

 strongly developed spines of the arms, in several (usually 4) alternating longitudinal rows 

 (comp. fig. 14). Those in the exterior row are (see fig. 12) fixed just where the dorsal skin 

 of the arm connects itself with the ambulacral skeleton, and in the basal part of the arm 

 always at the extremities of the calcareous transverse ribs; they are the longest of all, and 

 directed outwards to the sides; while those in the other rows decrease rapidly in length, 

 and are directed more downwards. Those in the innermost row (fig. 14. 4) are very small. 



