﻿ASTROPIIYTON CLAVATUM. 



191 



Astrophyton clavatum Lyman. 



Ti-ocoud. Kostoii Soc. Nat. Hist., VIII. p. 80. 18(11. 



Sjjecial Marks. — Radial ribs closely beset with minute, thorny 

 stumps or spines. 



Description of a Specimen. — Diameter of disk, 30°""- ; width of arm 

 at first fork, 12""° ; length of arm, 231'""-. 



Tooth-papillae and teeth aljout thirteen, regular, cylindrical, tapering, 

 sharp, the upper ones largest, the longest 1.5™"'. Mouth-papillEe about 

 four on each side, very small, somewhat irregular. Madreporic shield 

 lying at the corner of the interbrachial space, broader than long, plainly 

 made up of irregular, short, thickened tubes, soldered side by side. 

 The space occupied by the tentacle-pores and the covered under arm- 

 plates is sunken, forming a shallow trench, the joints being indicated 

 by obscure cross lines. Beyond the disk the joints are marked by 

 depressions between them, their outer and inner ends are thickened on 

 the sides, making a series of very distinct double ridges along the sides 

 of the arm. The under side of the arm, within and near the disk, is 



