INVERTEBRATES. 223 



general outline, but provided with a fifth very obtuse angle in 

 the middle below, and having each inferior lateral angle 

 slightly truncated. First radial pieces larger than the subra- 

 dials, and wedged so far in between them as to come nearly in 

 contact with the base, as wide as long, and heptagonal in out- 

 line, the sides connecting with the subradials being longer than 

 the others. Second radials smaller than the first, about as long 

 as wide, hexagonal in form. Third radials of the same size as 

 the second, heptagonal, and supporting on their superior sloping 

 sides the first secondary radials, each of which is succeeded by 

 another, the last of which bear on their inner sides above, 

 the delicate pendulous arms, and on the outer sloping sides 

 above, one or two pieces forming the bases of the false arms. 

 The first interradial and first anal pieces rest upon the broad, 

 superior, truncated side of the subradials, which they nearly 

 equal in size. They are all hexagonal, the inferior edges being 

 generally longer than either of the others. Above these, there 

 are in the second range three, in the third three or four, and 

 in the fourth three pieces, the latter being surmounted by three 

 or four others; all the series diminishing gradually from below 

 to the summit. 



The interaxillary pieces are all very small, two of them 

 being wedged down, one upon the top of the other, in the nar- 

 row space between the first and second secondary radial pieces, 

 while the others are arranged above, so as to form the upper 

 and inner sides of the two small apertures; the outer and lower 

 sides of which are formed partly by a sinus in the edge of the 

 second secondary radial pieces, and partly by one side of the 

 third. 



The secondary radials diverge so that those belonging to 

 each of the different rays (a a of diagram) meet over the 

 centre of each interradial space, where they support the false 

 arms. The first false arm pieces are not quite free, being 

 flanked on either side by the interaxillary pieces forming the 



