47 



radials, which gives to this ray two arms. There are, there- 

 fore, sixteen arms in this species. The arm formula is 4+3 + 



2+4+:i. 



The azygous area is substantially like the otliers. The first 

 interradials are the largest plates in the calyx, have nine sides 

 and are broadly truncated for the second interradials. The 

 .second interradials are more than half as large as the first, 

 and are followed by three plates in the third range, the middle 

 one only abutting upon the third ones, while the lateral ones 

 form part of the covering for the ambulacral channels. The 

 third range unites with two elongated plates belonging to the 

 vault. 



The vault is only slightly convex, and is covered with a few 

 large nodose plates. The azygous orifice is at the summit of 

 a short elevation, at the central part of the vault. There aie 

 twenty small ovarian apertures. 



This species is distinguished from all other sixteenarmed 

 species by its general form and surface ornamentation, and 

 also from all of them by the arm formula. For example, the 

 arm formula in D. ccdaiiis is 4 + 4+4+2+2, in D. nodostis it is 

 4+3+3+3+3, in D. snlehrosus it is 4+3+2+3 + 4, in A ham- 

 melli it is 4+3+3+3+3, and in D. arrosiis it is 4+4 + 3 + 3 + 2. 



Pound by (leo. K. (Jreene in the Hamilton (Irou]^, near 

 Charlestown, Ind., and now in the collection of Wm. V. E. 

 Gurley. 



DOLATOCRINU.S ASPEH, n. Sp. 



Plate 111; Fig. 10, basal view; Fig 11, summit vieio; Fig. 12, 



azygns side view. 



Species medium or rather below medium size. Calyx sub- 

 hemispherical, broadly truncated, and constricted below the 

 arms. Radial ridges snuill, sluirply angular, and bear a lon- 

 gitudinal sharp node at the middle of each plate. Ridges ra- 

 diate from a node at the center of each plate. Column round 

 and bears a cinquefoil central canal. 



T^asal ])lates forin a hollow cone within the cavity of Ihe 

 calyx. The column fills the cone .so t,hal the diameter of the 

 cf)lumn is nearly equal to the diameter of the pentagonal basal 

 disc. First priraai-y radials nearly or quite as long as wide 



