NATURAL SCIENCES OF PHILADELPHIA. 315 



high, and presenting a trigonal general outline, though the lateral 

 angles are doubtless minutely truncated. First radial pieces of 

 moderate size, heptagonal in form, and wider than long; second 

 and third a little smaller, the second being hexagonal, and the third 

 pentagonal, and supporting on its superior sloping sides the first 

 divisions of the rays. Secpndai-y radial or supraradial series 

 each composed of from eight to eleven pieces, rapidly diminishing 

 in length upward to the second bifurcation or commencement of 

 the arms, just below which a few of the smaller pieces seem to 

 be free and bear pinnulfe on their inner sides; farther down, the 

 second and fourth secondary radials of each ray give off, alter- 

 nately on each side,; small divisions that do not become free, 

 but are soldered into the interradial walls, though they can be 

 traced to the summit of the body, where they merely give origin 

 to pinnules. 



Anal area a little wider than the interradial areas. First anal 

 plate of about the same size as the first radials, hexagonal in 

 form, and supporting in the next range three pieces, arranged with 

 the middle one higher than the others; while, above these, three 

 smaller pieces can be seen arranged in the same way in the third 

 range, and three to four or five in the fourth, which is as far up 

 as they can be traced. The middle plates of this series form a 

 direct vertical row, that have a rather prominent mesial, rounded 

 ridge extending all the way up from the middle of the lowest 

 piece, of about the same size as those passing up the primary and 

 secondary radial series, while the other plates on each side and 

 other parts of the lowest pieces are ornamented with radiating 

 costse of smaller size, like those on the interradial pieces. 



Interradial areas not excavated below, but becoming moderately 

 concave above ; first interradial pieces of about the size of the 

 second primary radials, hexagonal in form, and supporting two 

 other somewhat smaller pieces in tlie next range, that bear between 

 their superior sloping sides a fourth smaller piece, while above 

 these there are two pieces in the next range that connect with 

 the pieces of the little lateral divisions of the secondary radials, 

 and perhaps some other small intercalated pieces filling the upper 

 part of the interradial areas. 



Axillary areas flat, and each occupied below by a hexagonal or 

 heptagonal piece of about the size of the second piece of each 



1872.] 



