100 NEW YORK STATE MUSEUM . 



The radials are thus seen to be unsymmetrical, supporting one 

 or two more plates on their right sides than on their left. This 

 has turned the apex of each plate to the left and through the 

 bibrachials has moved the distal or outer end of each ambula- 

 crum from 7 to 10 degrees from its expected position, as is shown 

 in plate i, lower figure. The center of this figure was found by 

 extending inwardly the lines marking the suture between each 

 pair of radials. The position of these lines extended outwardly 

 is marked on the circle nearly surrounding the figure. 



The proximal portions of the radials are gradually bent upward 

 [pi. 4. k] to form an angle of 90 degrees with a line across the 

 base of the theca. They thus together form a deep conical pit 

 or crater whose outer rim is a little more than twice the diameter 

 of the stem but which gradually becomes narrower as it pene- 

 trates the theca and brings the thin, inner portions of the plates 

 against the stem at a depth of seven or more of the stem rings. 

 The outer or distal portion of the radials is bent upward at an 

 angle of 30 degrees with the line across the edge of the crater 

 and this portion of the plate (one third or less of its length) 

 is from 1 to 2 mm in thickness at the suture or from three to 

 six times the thickness of the edge next the basals. An excep- 

 tion to this thickness is made where the radial meets the smallest 

 interbrachial plate of the lower row; here the thickness at the 

 edge is markedly reduced, as shown in plate 4 at i. 



Each plate shows a raised central mound on the rim of the 

 crater, carrying this rim outward a little and giving it a some- 

 what pentagonal figure. From this mound, or just above it, 

 there radiate some 10 or 20 depressed grooves, the more nearly 

 transverse ones being the deeper and together making a marked 

 transverse depression a little below the apex of each plate. The 

 more marked of these lines run across the suture and either 

 across or between the lower line of interradials. The portion 

 of the plate forming the inside of the crater is ornamented by 

 some fine rounded labyrinthine ridges as in plate 4, g, or a dew- 

 drop pattern as at h. The inside surface of these plates is 

 smooth with sometimes a raised central, longitudinal ridge at 

 the bend; probably representing attachment of viscera [pi. 4, i 

 and j]. The largest radial so far found measures 10.48 mm 

 across at greatest diameter or very nearly twice the diameter 

 of the radials of the specimen figured in plates 1, 2 and 3. This 

 plate [pi. 4, a] shows less ornamentation than the others but 

 the radials seem to vary rather markedly in this respect. Fig- 



