A. E. Verrill — North American Ophiuroidea. 309 



a. — Disk covered with scales above and below. 



h. — Disk-scales thin and nearly even. 



c. — Outer oral papilla flat or squamiform, usually with a small 



supplementary papilla by its side. Arm-spines 3 to 5, short 



and stout. 



A. incisa Lj^^m., '83. Arm-spines 3 ; radial shields wide. Disk- 

 scales large. 



A. Eugenice Ljung., '66. Arm-spines 4 or 5. Brazil. 



ec. — Outer oi*al papilla spiniform, prominent. 

 d. — Arm-spines slender, tapered. Radial shield wedge-shaped, 



divergent. 

 e. — Arm-spines 4 or 5 ; lowest one longest, bent. Disk-scales 

 minute. 



A. complanala Ljung., '66. Brazil. 



ee. — Arm-spines 6 to 8, nearly equal, two or three lower ones 

 usually bent. Disk scales not minute, regular. 



A. Otteri Ljung., '66. Maine to W. Indies, Portugal. 



dd. — Arm-spines 5, short and stout, beaked. Disk-scales minute, 

 obscure beneath. Radial shields narrow, touching distally. 



A. Palmeri Lym., '82. West Indies. 



hh. — Disk-scales irregular and swollen. Arm-spines 8. Outer 

 mouth-papilla spiniform, 



A. crassi^yes Ljung., '66. Brazil. 



aa. — Disk naked beneath, or with rudimentary scales only. Radial 

 shields narrow, elongated. Semilepis Ljung., "71. 



f. — Arm-spines 4 or 5, stout, subequal. 



A. semiermis Lym., '69. W. Lidies. 



jy. — Arm-spines 6, tapered, lowest longest. 



A.flexuosa Ljung., '66. Brazil. 



BB. — Tentacle-scale only one to each pore. Arm-spines 3 to 6. 

 Radial shields divergent, the distal ends sometimes touch- 

 ing, usually subovate or "pear-seed shape." A small sup- 

 plementary papilla or "oral scale " often stands by the side 

 of the outer oral papilla or oral scale. 



