A. JS. Verrill — Worth American Ophiuroidea. 325 



O. sciitata Lym. Arm-spines eight to ten, long, decidedly thorny. 

 Basal tentacle-pores with two flat scales; one, and spiniform, farther 

 out. Three tooth-papilla3. Disk-scales covered with small, thorny 

 crotchets. A pair of papillae on first under arm-plate. 



gg. — Basal rows of spines not closely approximate dorsally. Disk 

 with short thorny stumps. 



0. stellata Lym. Arm-spines seven, very thorny. Three conical 

 oral papillae. One tooth-papilla. , 



CC. — Disk entirely covered with tapered spinules or true spines, or 

 having more or less of them mixed with granules or other 

 structures, or else covered with granules only. 

 h. — Disk covered with spinules only, or else having spinules 



mixed with other structures, not granulated. 

 i. — Disk with spinules only or mainly. 

 /. — Dorsal rows of spines approximate dorsally. 



*0. spectahilis Sars. Arm-spines six to eight, serrulate. Disk 

 with tapered spines and some small conical stumps. Tooth-papillae 

 and distal oral papillae clustered. 



jj. — Basal rows of spines not approximate dorsally. 

 Jc. — Arm-spines finely serrulate, not glassy. Tooth-papilla single. 

 Oral papillae in a simple row. 



O.segestaJjjm. Arra-spines tapered, nearly smooth. Disk-spines 

 small, slender, smooth, mixed with few crotchets and thorny stumps. 

 Tentacle-scale single, small, acute. Oral papillae three, conical, all 

 similar. 



* 0. crassidens Ver. Arm-spines short, stout. Oral papillae and 

 teeth large and thick, rough. Disk with small, acute, conical spin- 

 ules. 



kk. — Arm-spines thorny and glassy. Disk-spines slender, thorny, 

 acute ; several tooth-papillae. 



O. pecthvula Ver. Outer edge of dorsal arm-plates with a row of 

 small acute serrations. Several distal oral papillae. 



ii. — Disk bearing few tapered spines mixed with other structures. 



Rows of spines approximate dorsally. 

 I. — Disk covered with granules mixed with a few tapered spines. 

 Arm-spines finely serrulate or nearly smooth. 



