198 s. GOTO : 



Adamhulacrals. — There are about 5 adambnlacrals to every 4 

 of the inferomarginals in the greater part of the arms. The 

 ambulacral groove is rather shallow and well open. Of the ad- 

 ambulacral spines, three stand at the farrow edge, the middle 

 one being the longest and all three fairly long and slender (PI. 

 Ill, fig. 56). Next come a pair, of which the abcentral one is 

 very much larger than the other, and more or less inflated at the 

 base, so that the general form is somewhat triangular. Then 

 follow a variable number (3-7) of small but rather thick spines, 

 of which one may be larger than the others. 



Mouth-plates. — In denuded specimens the mouth-plates are 

 very prominent, and the secondary ridge is barely noticeable. On 

 the principal ridge at least two more or less irregular rows of 

 tubercles are present (PI. Ill, fig. 56). In very small specimens 

 of 12 mm. E the principal ridge bears two rows of spines, six or 

 seven large ones on the crest, and five or six on the outer side ; 

 the one at the mouth end being conspicuously larger than the 

 others. The secondary ridge bears at this stage one, two or three 

 spines. In larger examples the general arrangement of the spines 

 remains the same, but the two rows on the main ridge become 

 more or less duplicated and irregular, and the spines are more 

 numerous, there being some twenty larger spines and some sixteen 

 smaller ones. On the secondary ridge there are now 6-8 spines, 

 but they always lie in a single row. The spines of the secondary 

 ridge and the terminal ones of the main crest form a row along 

 the ambulacral furrow. 



Ventrolaterals. — The ventrolaterals are small, and there are 

 usually 2 or 3 on either side of the interradial line (PI. Ill, fig. 

 56). 



