36 



to show all the plates, and, for the same reason, there is a little 

 doubt about the number and shape of some of the plates just 

 below the top of the calyx. 



The first secondary radials are nearly as large as the third pri- 

 mary radials. In one of the lateral rays on each side there are no 

 tertiary radials. In each of these two rays the second secondary 

 radials are somewhat smaller than the first and extend to the 

 lower part of the commencement of the enlargement for the arms. 

 There are three or four more plates in each series, forming the 

 base of the arms, before the arms become free. This gives us five 

 or six secondary radials in each series, and two arms to each of 

 these rays. In the other three rays there is only a single sec- 

 ondary radial in each. It is pentagonal and supports upon each 

 of the upper sloping sides tertiary radials. There are four or five 

 tertiary radials in each series, the last three or four of which form 

 the base of the arms before they become free. The last two or 

 three plates in each of the radial series are more or less cunei- 

 form before the arms become free. There are, therefore, four 

 arms to each of three rays and two arms to each of the other two 

 rays, making in all sixteen arms to this species. The arms are 

 composed of a single series of cuneiform plates. 



In the interradial areas there is one hexagonal plate separating 

 the second primary radials, and two plates in the second range sep- 

 arating the third primary radials, each of which is about the size of 

 the primary radials. There are three plates in the third range, three 

 in the fourth and three in the fifth; the last form a sharp ridge 

 between the arm bases, which rises above the vault plates, that 

 abut against it. In the intersecondary areas there is one plate in 

 the first range and two in the second; the latter form a sharp 

 ridge between the arm bases, which rises above the vault plates 

 that abut againsHt. First azygous plate in line with the first 

 primary radials and^of the same size; it is followed by three plates 

 of the same size as the first radials. Above these the area and 

 arrangement of the plates is very much like the regular areas, 

 with about one more plate in each range. 



The vault bears a large central plate with a big conical spine. 

 There is also a spinous plate over the junction of the ambulacral 

 furrows in each series, making six spinous plates on the vault. 

 The plates that cover the vault are polygonal and of very unequal 



