ASTROPHYTON CLAVATUM. 



lUl 



Astrophyton clavatum Lvman, 



Proceed. Buston Soc. Nat. Hist., VIII. p. XJ. 1H(JI. 



Sjyecial 3Ic(rks. — Kiulial ril)s clo.sely l)e.set ^vitll minute, thorny 

 stiiiiip.s or spines. 



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

 at first fork, 12""" ; length of arm, 2:51 "'"'■. 



First joint (within the disk) to second 8"""- 



Second " *' third, 12 " 



Third " " fourth, 8 " 



Fourth " " fifth, U " 



Filth " " sixth, 11 " 



Sixth " " seventh, 11 " 



Seventh " " eighth t> " 



Eighth " " ninth, 10 " 



Ninth " " tenth, 12 " 



Tenth " " eleventh, . . . . 10 " 



Eleventh " " twelfth 11 " 



Twelfth " " thirteentli, .... 11 " 



Tiiirteenth " " fourteenth, . . . . 11 " 



Fourteenth " " fifteenth, .... 7 •' 



Fifteenth " " sixteenth, .... 9 " 



Sixteenth " " seventeenth, ... 9 " 



Seventeenth " " eighteenth, .... 9 "• 



Eighteenth " " nineteenth, .... 8 " 



Nineteenth, '' " twentieth, .... 8 " 



Twentietli '' " twenty-first, ... 8 " 



Twenty-first " " twenty-second, ... G " 



Twenty-second " " twenty-third, ... 9 "■ 



Twenty-third " " twenty-fourth, ... 5 " 



Twenty-fourth " " twenty-fifth, ... 8 " 



Twenty-fifth " " twenty-sixth, ... 5 •' 



Twenty-sixth " " twenty-seventh, . . 5 *' 



Twenty-seventh •' " twenty-eighth, ... 5 " 



Twenty-eighth '■ " end, 5 " 



Totallength, 239""''- 



Tooth-papilla) and teeth about thirteen, regular, cylindrical, tapering, 

 sharp, the upper ones largest, the longest 1.5'""-. Mouth-papilhi) about 

 four on each side, very small, somewhat irregular. Mudreporic 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. Bejond 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 



